Dogs and cats can develop diabetes mellitus, commonly referred as simply “diabetes,” the same as their human counterparts can. Diabetes is more complicated than merely having high blood sugar and can seriously impact our pet’s overall health.
As part of National Pet Diabetes Month in November, The Meowing Vet explains the causes, signs, and therapies of diabetes mellitus as well as the ramifications that uncontrolled diabetes can incur in our dogs and cats.
Read below for detailed information…
What is diabetes mellitus? What are the two types of diabetes?
Both dogs and cats can develop diabetes. In the most basic of definitions, diabetes mellitus (DM) is an endocrine disorder (or endocrinopathy) in which the blood glucose (BG) level in the bloodstream is too high (i.e. high blood sugar, or hyperglycemia). Because cells across the whole body use glucose, a simple sugar molecule broken down from carbohydrates in food that your pet consumes, diabetes affects the entire body: the GI tract, the cardiovascular system, the urinary system, and the nervous system including the brain. Thus, diabetes mellitus is a whole lot more complex than just having high blood sugar.
Why does blood sugar get too high with diabetes? Because the body either does not produce enough of the hormone insulin or the body’s cells cannot respond the effects of insulin that tell them to take up glucose from the bloodstream. (You’ll learn more about the role of insulin in the next section below.)
The first scenario in which the body (specifically, the pancreas) does not produce enough insulin is known as type 1 (or insulin-dependent) diabetes mellitus. This diabetic type is often called “juvenile diabetes” in humans. Type 2 diabetes mellitus is described by the second scenario in which the pancreas produces insulin normally, but the body’s cells resist insulin’s action to allow glucose from the blood to enter. Therefore, type 2 diabetes is also termed insulin-resistant or non-insulin-dependent diabetes mellitus. Type 1 diabetes is more common in dogs while type 2 diabetes occurs in cats and has not been reported in canines.
Dogs at any age may be affected. Un-spayed female dogs are more at-risk. Canine breeds at increased risk of diabetes development include poodles, dachshunds, miniature schnauzers, English springer spaniels, miniature pinschers, and many terrier breeds. Older cats over 10 years of age are more likely to develop diabetes, though younger cats may also be affected. Neutered male cats are more commonly affected in relation to female and intact male cats. Any cat breed may develop diabetes although Burmese cats in Australia may be genetically predisposed.
Though having a pet that is overweight or obese can complicate the management of both forms of diabetes, type 2 diabetes cases tend to develop as a direct consequence of obesity rather than type 1 diabetes, which develops secondary to destruction of the insulin-producing cells of the pancreas.
Check out these 5 Facts on Diabetes by veterinarian Dr. Leigh on her website My Vet + Me!
What is the role of the pancreas? Why is insulin so important?
The pancreas is an organ located in the abdomen near the stomach, liver, and small intestine. It plays an important role in both the digestive and endocrine systems. Not only does the pancreas produce enzymes that help break down food to allow for nutrient usage, but the pancreas also produces important hormones that function in the endocrine system: glucagon and insulin. The endocrine system is made up of various organs and tissues that produce hormones, which travel throughout the body to send signals to various cells and tissues, allowing different organs to communicate with one another.
Glucagon and insulin are two pancreatic hormones that do just this. Areas of endocrine cells in the pancreas are clumped together in regions called islets of Langerhans. Special alpha-cells (α-cells) in these regions produce glucagon, which is released into the bloodstream by the pancreas when it’s been awhile since your pet’s last meal and blood sugar is getting low. Glucagon triggers stored glycogen, fat, and protein to be converted into glucose via a process known as gluconeogenesis to raise blood sugar. (If stored fat receives glucagon’s signal to serve as a fuel source, it is transformed by the liver into molecules known as ketones. Tuck this nugget of information into the back of your head as ketones will come into play later in this article.*)
Glucagon works in opposition to insulin to maintain a steady blood glucose (blood sugar) level roughly between 80-120 mg/dL in dogs and cats (different laboratory measurements may slightly vary). Insulin is produced by another specialized cell type known as beta-cells (β-cells), which normally release insulin into the bloodstream following a glucose-rich (or sugar-rich) meal. Insulin release thereby lowers blood sugar by causing glucose to enter cells to serve as a fuel source, allowing for cellular reactions to keep the body functioning healthily.
With type 1 diabetes mellitus, the beta-cells are damaged and cannot produce and release insulin normally. In type 2 diabetes, the beta-cells may be functioning normally and be producing adequate amounts of insulin, but the body’s cells become resistant to the action of insulin, thus casting a “deaf ear” to insulin’s signals to take in glucose and thus lower blood sugar. Both types of diabetes result in high blood glucose without a means to get that sugary fuel source into cells. The fuel is there, but the body’s cells starve nonetheless. Your diabetic dog or cat may feel like he or she is ravenous, but without adequate insulin production and cellular reception of glucose, eating more will not help feed the body’s cells and tissues and may even worsen this endocrine imbalance without other medical therapies. Such therapies include supplemental insulin injections, as well discuss in length below.
What causes diabetes mellitus?
Causes of Type 1 (insulin-dependent) diabetes in dogs (and some cats)
- Autoimmune destruction of pancreatic beta-cells (i.e. your pet’s own immune system attacks itself to destroy insulin-producing cells of the pancreas): This may be congenital (meaning your puppy is born with type 1 diabetes) or be acquired later in life, sometimes with potential genetic influence, as a consequence to viral infections, or otherwise idiopathic (of unknown cause). The degree of beta-cell destruction may vary between patients.
- Pancreatitis: Pancreatitis is inflammation of the pancreas, often secondary to the consumption of rich, fatty, greasy foods such as ham. Pancreatitis causes leakage of the pancreas’s digestive enzymes, which cause the pancreas to “digest itself” in a matter of speaking, causing painful inflammation and damage to the pancreas. If severe enough, pancreatitis can cause long-standing destruction to the pancreas, including to the beta-cells that normally secrete insulin, in turn triggering the onset of type 1 diabetes mellitus.
- Hyperadrenocorticism (Cushing’s disease): In a nutshell, Cushing’s disease (which more commonly affects dogs rather than cats) occurs when the body’s adrenal glands produce too much cortisol, a stress hormone normally released during the “fight-or-flight” response. Cortisol triggers a cascade of events that raise blood sugar to give a burst of energy to your stressed dog or cat. If your pet has Cushing’s disease, his or her body will be under a constant state of stress due to excessive cortisol influence, which impairs the regulation of normal blood glucose and insulin levels. High doses of chronic steroid use (such as prednisone or prednisolone) can induce an iatrogenic hyperadrenocorticism, which can also lead to or complicate pre-existing diabetes mellitus.
Hypersomatotropism/acromegaly: Increased levels of growth hormone (a.k.a. somatotropin) produced by the pituitary gland can trigger the development of diabetes mellitus by disrupting hormonal production and signalling. These patients (typically cats) may actually gain weight despite being an uncontrolled diabetic.- Progesterone: Progesterone is an important sex hormone, of primary significance in the heat cycling of females and in maintaining a healthy pregnancy. However, progesterone can also raise blood sugar levels and deregulate insulin production and action. Therefore, intact (i.e. un-spayed) female dogs are more at risk of developing diabetes than are spayed female or male dogs. Pets who are prescribed progesterone supplementation for various health reasons or breeding purposes may also develop diabetes mellitus as an unwanted side effect.
- Pregnancy: Due to hormone influence, including high progesterone levels as addressed above, gestational diabetes can develop in both pregnant humans and dogs.
Causes of Type 2 (insulin-resistant) diabetes in cats
- Obesity: Obesity is defined as having a heavy body weight due to excessive fat deposits secondary to the increased storage of excess energy from food consumption that the body cannot expend at that particular time. However, fat isn’t just a sedentary layer for energy storage and insulation; it is an active endocrine organ that influences blood sugar and insulin regulation and can lead to cellular insulin-resistance and thereby type 2 diabetes mellitus over time.
- Hyperadrenocorticism (Cushing’s disease): see above
- Hypersomatotropism/acromegaly: see above
- Progesterone therapy: see above
What are the clinical signs of diabetes mellitus in pets?
Be suspicious of diabetes mellitus and converse with your personal veterinarian if you observe the following signs in your dog or cat:
- Weight loss despite a hearty appetite (polyphagia): Remember, even if your diabetic pet eats nutritious meals, he or she cannot use those nutrients as fuel, so the body remains in a state of starvation despite consuming enough food.
- May be either very thin with muscle wasting or else obese
- Increased urination and increased thirst (polyuria and polydipsia, or PU/PD, respectively): The kidneys function to maintain a healthy volume of water and electrolytes in the bloodstream by controlling the amount of fluid and other substances that go into urine. The kidneys also act as a selective sieve to keep in good elements in the bloodstream (like nutrients) while scrubbing out toxins to be removed from the body in urine. Normally, the kidneys keep nutrients such as glucose in the bloodstream rather than removing them to be incorporated in urine. However, in cases of diabetes mellitus, the blood glucose level may become so high that it exceeds the threshold at which the kidneys can no longer prevent all that sugar from leaking out of the bloodstream into urine. Therefore, excess glucose is dumped into urine (i.e. glucosuria). However, sugar attracts water, so moisture follows, and a larger volume of urine is produced. Therefore, diabetic pets tend to urinate larger volumes more often than non-diabetic animals; this is termed polyuria (PU). To prevent dehydration since more water than normal is being lost from the bloodstream into the urinary tract, the diabetic patient must take in more fluids to compensate for this loss. Thus, diabetic pets also display excessive thirst, called polydipsia (PD). You may notice that you’re having to clean up urinary accidents in your home or re-fill your dog or cat’s water bowl more often; these are signs of PU/PD and should be addressed with your vet.
- Cloudy eyes and visual impairment or blindness due to cataract formation (dogs only)
- Skin and coat changes:
- Dogs: fur loss (alopecia), greasy skin (seborrhea), skin infections (pyoderma), patches of thickened/crusty skin (hyperkeratosis)
- Cats: unkempt hair coat
- Abnormal stance or gait (may be scuffing a foot when walking or standing abnormally)
How is diabetes mellitus diagnosed?
After listening to your description of the abnormal clinical signs that your pet is displaying at home and after noting physical examination abnormalities consistent with diabetes, which may include an enlarged liver, your veterinarian will wish to run additional tests to check for diabetes. High blood pressure (hypertension) may also be detected in some diabetic dogs.
Necessary tests include bloodwork and a urinalysis, which will predominately show high blood glucose (hyperglycemia) and oftentimes evidence of glucose spillover in urine (glucosuria), respectively. Elevated liver enzymes may be noted on bloodwork, and trace levels of ketones may be detected in urine. Blood may also be lipemic, or contain an increased amount of fats called triglycerides. Some vets may run further blood tests such as fructosamine or A1c. In a way, these tests measure blood sugar in reverse, granting an idea of what the average blood glucose level of your pet has been over the past few months. These tests may be useful in providing a baseline when your dog or cat is first diagnosed with diabetes, but they are not without their flaws. These tests are not as accurate in our pets as they are for use in diabetic humans. That being said, fructosamine may be somewhat useful for monitoring the success of insulin therapy in felines who become too stressed to stay in-hospital to allow for a blood glucose curve. As we’ll explain below, the blood glucose curve is the best method for vets to monitor how well your pet’s blood sugar is responding to the prescribed diabetic treatment.
Learn how to interpret your dog or cat’s bloodwork and urinalysis results with The Meowing Vet’s past articles.
Can diabetes mellitus be treated? If so, how?
Once a firm diagnosis of diabetes mellitus has been reached, your vet will have a long discussion with you about the multiple areas of therapy required to manage your pet’s diabetes. I understand firsthand how overwhelming it feels when a pet is newly diagnosed with diabetes. Before I was a veterinarian, my cat Tolstoy was diagnosed with type 2 diabetes. He has been managed on a prescription diabetic cat food as well as bi-daily insulin therapy. Now six years following his diagnosis, he is fortunately faring quite well! However, his management and rechecks have been time-consuming and costly over the years yet well worth it.
Treatment modalities for managing diabetes mellitus
Insulin therapy: We’ll delve into the ins-and-outs of insulin types later on , but by now you’ve probably gathered that insulin supplementation is imperative in this whole diabetic management thing. Unfortunately, insulin cannot be taken orally as it is destroyed by gastric acid in the stomach before it has a chance to be absorbed and work systemically to reduce blood sugar. Therefore, it must be administered via injections and is dosed in units. Insulin is most commonly administered twice daily (every 12 hours) at the time that a meal is fed, but once daily insulin therapy may be successful in some animals.- Oral medications?: Though some oral medications are used with good results in diabetic human patients, most oral diabetic drugs are not very useful in dogs and cats. Such medications may work either by decreasing cellular resistance to the effects of insulin in cases of type 2 diabetes or by altering hormonal regulation that thereby affects blood glucose levels. Though these medications are largely not effective in most diabetic pets, some cats may respond well to glipizide, an oral hypoglycemic drug that helps the pancreas produce more insulin. Up to 15-20% of cats may respond well to glipizide, but most require insulin therapy instead. Glipizide may be considered in otherwise healthy diabetic cats whose owners absolutely cannot administer insulin injections. Another oral medication called Bexacat was approved by the U.S. FDA in 2022 and boasts increased effectiveness at managing blood sugar for 80% of cats.
Prescription diet specially formulated for diabetics: These diets have a lower glycemic index (i.e. lower in simple carbs) and are also lower in fat to help regulate blood sugar and prevent drastic spikes and crashes in blood glucose levels. Therefore, an excess of simple carbohydrates (sugars) should be avoided (including white rice). For dogs, good quality protein and fat should be maintained in moderate amounts; for cats, a high protein diet is essential. Many prescription diabetic diets are often higher in soluble and insoluble fiber to aid glycemic control and keep pets feeling fuller, but you may notice increased flatulence (gas) in your pet if fed a high-fiber diet. Various veterinary pet food brands offer such specialized diets, so ask your veterinarian which one best suits your pet’s nutritional needs. Canned wet food or dry kibble are available for most brands.
- Canine options: Royal Canin Glycobalance, Purina EN Gastroenteric Fiber Balance (formerly Purina DCO), Hill’s w/d
- Feline options: Cats newly diagnosed with diabetes should start on a low starch diet (Royal Canin Glycobalance or Hill’s m/d) and then transition slowly over 4 weeks to a fiber-enhanced diet (Hill’s r/d or w/d) for maintenance. However, if your cat is obese, your vet may opt immediately for a fiber-enhanced diet to facilitate weight loss. If, however, your cat’s blood glucose continues to be poorly managed or if uncontrolled weight loss continues while on a fiber-enhanced diet, a switch back to a low starch diet may be recommended for either the short or long term. If a prescription diet is outside your price range, your vet may recommend Fancy Feast Classic Pate canned food, a more affordable commercial diet with very low carbohydrate content; make sure you’re choosing the pate option and not a selection with gravy as gravy is high in carbs.
- Weight management: Helping your overweight or obese pet to shed extra lbs through a healthy diet and exercise program is vital for diabetic management. This dietary regimen also means restricting treats and most human foods. Some overweight cats who are promptly diagnosed and treated for diabetes may even go into remission (or a non-diabetic) state if they maintain a healthy weight. (Click here for some healthy ideas to help you safely reduce your pet’s waistline.)
- Adhering to a strict schedule each day: Insulin injections, feedings, and exercise must be performed at the same time each day to best regulate your pet’s blood glucose levels, preventing hypoglycemia and reducing hyperglycemia.
- Provide your pet with plenty of fresh water
- Spaying your intact female dog: If you have an un-spayed female dog who has been diagnosed with diabetes, having her spayed will remove the influence of progesterone and greatly aid in the management of her diabetes.
The diverse world of insulin
As explained, insulin must be given in injectable rather than oral form and is administered on a strict schedule either every 12-24 hours as directed by your vet. There are various types of insulin categorized by their various lengths of duration (short, intermediate, or long) or species from which they originated (i.e. insulin molecules most similar to that of humans, pig, etc.). Short-acting insulins are used by veterinarians in hospital settings only, often for the critical management of diabetic ketoacidosis (DKA) cases (read more below). Instead, intermediate or long-acting insulins are typically prescribed for at-home use.
The most common insulins used in dogs include the intermediate-acting insulins Vetsulin® (a lente insulin derived from pigs yet identical to canine insulin), NPH insulins such as Humulin®-N or Novolin®-N (based on human insulin) as well as the long-lasting insulins PZI (or ProZinc®) and glargine (both are also based on human insulin). Some human-based insulins (such as Humulin® and Novolin®) are not recommended for cats as they vary significantly from feline insulin molecules. However, some cats fare well on PZI, which is also derived from human insulin. Blood sugar control in diabetic cats is most successful with long-lasting insulins such as PZI, glargine, or detemir although some do well with Vetsulin® use.
Insulin bottles should be stored in the refrigerator. Note the expiration date so that you can obtain fresh refills as necessary. A new sterile insulin syringe should be used each time your pet receives insulin, and the syringes should ideally not be filled too far in advance. Your vet will show you how to safely and accurately administer injections. An automatic insulin pen (VetPen®) may be used to facilitate pet owners who have a difficult time dosing their pet’s syringes; however, it is only usable with Vetsulin® type insulin.
Also keep in mind that different insulin types should be handled differently. For example, most insulins should be rolled gently and should not be shaken to prevent breaking up the insulin molecules. An exception to this rule is Vetsulin®: its bottle should be shaken firmly prior to drawing up insulin in a syringe to ensure that its unique formula is well-mixed and that each syringe draws up a uniform amount of insulin from the bottle’s suspension.
One of the most important things to consider with insulin administration is that you are using the correct insulin syringe. There are two main types of insulin syringes: U-100 and U-40, based on the number of units and the volume sizes of each unit within the syringe. Always confirm with your vet as to which type of syringe you should be using with the type of insulin that your pet was prescribed. It can be dangerous to use the incorrect syringe size with a particular insulin type. For example, U-40 syringes should be strictly used with Vetsulin® and PZI while the NPH insulins Humulin®-N and Novolin®-N are dosed with U-100 syringes. Lesson learned: always read the label!
And lastly, if your vet has called in your pet’s insulin prescription to a human pharmacy, always ensure that your pharmacist is adhering to your vet’s instructions. For instance, make sure that you’re purchasing the correct syringe size if you’re obtaining your insulin syringes from the pharmacy rather than your local veterinary clinic. Bottom line: dog and cat insulin therapy is different from that of humans!
What are the dangers of not treating diabetes mellitus?
Dysfunction of the nervous system
Fortunately, most cells of the body, though they prefer to utilize glucose as a primary fuel source, can use proteins (amino acids) and fatty acids and their byproducts (such as ketones) as energy. However, the central nervous system (brain and spinal cord) can only use glucose as fuel. Therefore, maintaining proper blood glucose levels is vital for the brain, making diabetes mellitus very dangerous for nervous system health. Seizures can arise due to low blood sugar (hypoglycemia) due to rapid swings in blood sugar regulation as can sometimes occur in diabetics. Brain “fogginess” or impaired cognition can also occur in times of high blood sugar (hyperglycemia), causing your pet to appear confused or even agitated. Furthermore, impairment of the peripheral nerves going to the limbs can also be affected, leading to numbness of a limb, nerve tingling and pain, or impairment in walking which may manifest as scuffing the top of a paw (conscious proprioception deficits). Some diabetic cats may begin walking unusually by placing weight on the entirety of their back feet rather than just on their foot pads; this is known as a plantigrade stance (or “dropped hocks”). These phenomena are each called a diabetic neuropathy.
Urinary tract infections (UTIs)
As discussed previously, the kidneys can only hold back a certain amount of glucose from entering the urinary tract to be incorporated into urine. When blood sugar levels are high enough, some glucose molecules leak out into the kidneys and are stored in urine in the bladder (known as glucosuria). Glucose isn’t just an excellent fuel source for our pets; bacteria and fungi feast on it, too. Therefore, urinary tract infections (UTIs) may be more common in diabetic patients. The presence of a persistent UTI may also complicate the medical management of diabetes, especially in cats. Infections elsewhere in the body may be more likely to occur in diabetic patients.
Cataract development in dogs
As you know, cells use glucose as energy. In non-diabetic circumstances, the detection of high blood sugar by the pancreas leads to the release of insulin into the bloodstream, which travels to various cells in the body, alerting them that the blood is rich in glucose that the cells should pull in to utilize as energy (known as ATP, or adenosine triphosphate, the most basic building block used as energy by cells and comprised of glucose). A cell’s conversion of glucose into ATP, its usable form of energy, is called glycolysis; this process is started by an enzyme called hexokinase, which transforms glucose into a byproduct called pyruvate. (Bear with me. I swear this chemistry lesson is gonna tie back to diabetic cataract formation.) However, when blood sugar is too high (as occurs in diabetic patients), there’s too much glucose to be processed by the limited amount of hexokinase available in a cell, so other enzymes try to help out. Aldose reductase is one of these “helpful” enzymes. It gets to working on glucose and transforms it into sorbitol rather than pyruvate. If all goes well, sorbitol can be later altered to form another sugar called fructose, which can then be broken down into glucose again, starting over the process of fueling the body’s cells by creating ATP molecules.
However, this is diabetes mellitus we’re talking about here, so ya know that something’s not going to go right! Remember that all cells use glucose as fuel. This includes cells in the eye, including those around the ocular lens (the clear structure located in the pupil or center of the eye that allows light to shine through the retina at the back of the eye, allowing us and our pets to see). When a dog or person is diabetic and aldose reductase in the eye’s cells transforms excess glucose into sorbitol (due to an overwhelmed hexokinase pathway), things go awry. Sorbitol attracts moisture and draws in excessive amounts of nearby water, including around the lens of the eye. This excess moisture causes swelling of the lens fibers and affects the structural integrity of the proteins in the lens. This causes the lens to become cloudy, causing a cataract (or cloudy area of the lens) to develop. Cataracts block light from entering the retina, causing visual disturbances that may result in complete blindness.
In terms of our pets, cataracts only arise in dogs as a consequence of diabetes; cats do not develop cataracts secondary to diabetes (though they may due to other reasons). Cats do not have a large amount of aldose reductase in the ocular lens, so not much sorbitol is formed, preventing excess moisture absorption and cataract formation from developing in the eye.
Nearly half of all diabetic dogs develop bilateral cataracts (i.e. cataracts in both eyes) within 6 months of the onset of their diabetes; up to 75% of diabetic dogs will develop cataracts within one year, and over 90% will form cataracts within their lifetime. At this current time, no effective medical means of preventing or dissolving cataracts has been attained. Though studies regarding the use of ocular suspension drops to prevent aldose reductase activity have been conducted, none have been very successful to date. Instead, the only treatment method to resolve cataracts is via eye surgery, either via extracapsular extraction or phacoemulsification (a “phaco”). These procedures, performed by veterinary ophthalmology specialists, involve removing your pet’s cloudy lens and replacing it with an artificial lens that will not be affected by sorbitol. However, preventing cataract formation before it starts by effectively managing your dog’s diabetes is key.
Diabetic ketoacidosis (DKA)
The scariest consequence of diabetes mellitus for many veterinarians and pet owners is concern over the development of diabetic ketoacidosis, or DKA. DKA is a medical emergency that requires immediate and aggressive treatment by your veterinarian in order to save your pet’s life. Diabetic dogs are more likely than cats to develop DKA, though some feline patients may be affected.
*Earlier in this article when describing the hormones produced by the pancreas, we discussed the role of glucagon, which sends signals to stored fat reserves to begin transformation into a usable energy source for the body when blood glucose supplies are low or when glucose cannot be utilized by starving cells. When fat stores are converted into an energy source by the liver, molecules known as ketones are produced as a byproduct. Ketones are acidic molecules that may alter the delicate pH (or acid-base balance) of the bloodstream. DKA occurs in diabetic patients when ketones reach a high enough level to lower pH to a dangerously acidic state, thereby inducing a metabolic acidosis. A hyperosmolar state (or excessive “blood saltiness”) also develops. These conditions with secondary vomiting also cause severe dehydration and electrolyte abnormalities, depleting the body’s cells of vital sodium, potassium, and phosphorus. Patients rapidly become very ill, displaying the clinical signs discussed below:
Clinical Signs of DKA
If you observe these signs in your diabetic pet, seek immediate emergency veterinary attention!
- Decreased appetite
- Lethargy or collapse that may progress to coma or shock
- Vomiting (with or without diarrhea)
- Abnormally fast and deep breathing (known as Kussmaul respiration): When the body senses that it’s acid-base balance is off in a metabolic acidosis state, it tries to remove excess acid from the body. One compensatory method is to blow off excess acid from the lungs via expiration (exhaling), leading to quicker and deeper breaths as may be seen with DKA.
- May have yellowing of the skin and whites of the eyes (icterus or jaundice): due to red blood cell destruction (or hemolysis) secondary to low phosphorus levels in the blood
DKA is diagnosed in diabetic patients via clinical signs, bloodwork, and urinalysis (including a urine dipstick test which detects the presence of ketones in urine, i.e. ketonuria). Because DKA is often triggered by a concurrent illness afflicting diabetic patients that sends them over the edge, a further work-up, often involving radiographs (x-rays) of the chest and abdomen, is also warranted to find the inciting cause. Such diseases that may induce DKA in a diabetic patient include urinary tract infections (UTIs), pyometra, kidney disease, pancreatitis or exocrine pancreatic enzyme insufficiency (EPI/PEI), inflammatory bowel disease (IBD), hyperadrenocorticism (Cushing’s disease), heart disease, respiratory disease such as asthma, hyperthyroidism in felines, severe ear infections, and cancer.
Treatment of DKA involves hospitalization with IV fluids with electrolyte supplementation and vigilant insulin therapy as well as treating the concurrent illness that triggered the DKA. Diligent maintenance of your pet’s diabetes at home and managing their overall health are imperative to reduce the chances for DKA development.
The extremes of diabetes: hypoglycemia and DKA
Just like we want to prevent and/or promptly treat diabetic ketoacidosis (DKA) as quickly as possible, we also want to prevent your pet’s blood sugar from swinging too far to the other extreme, causing your pet to become hypoglycemic. Hypoglycemia (or low blood sugar) occurs when your pet’s blood sugar dips too low and is a danger when your pet’s blood glucose is below 50-60 mg/dL. This can occur due to complex hormonal fluctuations of glucose regulation as is impaired with diabetes mellitus; hypoglycemia can also occur if your diabetic pet misses a meal yet receives his or her insulin injection or may be the result of receiving too much insulin. If you find your diabetic pet weak, cold (hypothermic), unresponsive, or having a seizure due to hypoglycemia, try to safely rub some honey or Karo® corn syrup on his or her gums to raise blood sugar as you begin your journey to your closest veterinary clinic. Another sign of hypoglycemia in felines is cervical ventroflexion in which the affected cat is unable to raise his or her head; this may occur due to low potassium levels (hypokalemia) secondary to the effects of low blood sugar.
Many pet owners wonder whether or not their pet should receive his or her full insulin dose if he or she is not eating well one day. This is a tricky scenario. We don’t want blood sugar to remain too high for too long a duration without insulin therapy. However, we also don’t want to give too much insulin without a meal because hypoglycemia may result. Not only is hypoglycemia be troublesome in the present, but chronic hypoglycemia (especially overnight) can cause a very high rebound blood sugar the next morning, known as the Somogyi effect. This phenomenon completely skews the results of a blood glucose curve and makes insulin dosage adjustments difficult for your vet. Therefore, when a dog or cat doesn’t want to eat, your vet may advise that you administer half of your pet’s normal insulin dose and monitor your pet for the rest of the day. If he or she worsens or develops vomiting, DKA may have developed, requiring prompt medical attention. If your pet improves and begins eating and acting normally again at the next meal, then the normal prescribed insulin regimen can be resumed.
If your pet is to be fasted for some reason (i.e. for bloodwork or anesthesia), always consult with your veterinarian regarding whether or not your pet should receive his or her insulin injection for that day.
Why check-ups are so important
Initially, it may appear that your veterinarian wants to schedule rechecks quite frequently. This is because there’s so much to manage when medical therapy begins for a diabetic patient. Your vet wants to ensure that your pet’s prescribed insulin dosage is neither too high (causing hypoglycemia) or too low (thereby not exerting a strong enough effect to lower your pet’s high blood sugar). Or maybe your vet will determine that the type of insulin your pet is on should be changed to a better type. There is no “cookie cutter” when it comes to diabetic patients; each individual will vary as to which clinical signs they exhibit, their blood glucose levels, and response to therapy. Fortunately, the frequency of rechecks often decrease as your pet’s diabetes becomes better managed. However, to give your dog or cat the best chance to improve (and for your cat to possibly enter remission), rechecks and firmly adhering to your vet’s advice early on is vital, so please remain patient.
As mentioned prior, the blood glucose curve is an excellent tool in helping your vet understand how your pet’s blood glucose levels are fluctuating throughout the day. Via repeated small blood sampling obtained frequently throughout the day (often performed every 1-4 hours), your vet can graph your pet’s hourly blood sugar and can determine how effective and for what duration of time the prescribed insulin is working. The glucose curve will help your vet help your pet by ensuring the correct type and dosage of insulin are being used. Your vet may perform serial blood samples throughout the day in-hospital or else implant a small device called the FreeStyle Libre continuous glucose monitoring system for easier, flash monitoring (no repeated skin pricks!); your pet can even wear this device at home for up to several days rather than spending hours or days at your veterinary clinic!
The long-term prognosis of canine and feline diabetes mellitus
In most cases of diabetes, there is no cure and therapy is a daily, lifelong endeavor. Some feline patients can enter remission and be cured, however, particularly if their disease is detected early and prolonged hyperglycemia is avoided (to prevent glucose toxicity to the pancreas). Weight reduction in overweight cats, feeding prescription low-carbohydrate diabetic diets (especially canned formulas without gravy), and appropriate insulin therapy may allow roughly 10-25% of such well-managed cats to enter remission within 3 months, allowing them to discontinue insulin (some studies report higher remission rates). However, 25% of these cats may relapse, requiring long-term insulin therapy. Working closely with your veterinarian to perform regular physical exams and blood glucose curves is important to give your cat a chance of achieving this goal of a cure. Unfortunately, many diabetic cats fail to receive such regimented care. Sadly, most diabetic felines are euthanized within 1-2 years after their diagnosis because their owners are unable to successfully manage their diabetic needs. Other cats may go on to live longer (such as my beloved Tolstoy) while other may die due to complications involving their diabetes or concurrent diseases. For instance, diabetic cats with concurrent chronic kidney disease (CKD) have a poorer prognosis than diabetic cats with normally functioning kidneys. The management of diabetes is certainly complicated by the co-existence of other diseases.
Diabetic canines tend to fare better than cats overall and have an average lifespan of 2-3 years following diagnosis of diabetes. As in cats, management of diabetes in dogs involves weight management in overweight dogs, insulin therapy, and oftentimes a prescription diabetic diet (particularly high fiber diets so long as the dog is not underweight). Many dogs live comparatively longer than diabetic cats, but of those who die, most are euthanized due to the difficulty of managing their disease.
At-home diabetic monitoring
As a vet and fellow pet owner, I recognize how inconvenient and costly that frequent blood glucose curves can be for my clients. Glucose curves are primarily performed via glucometers, small devices that require just a small drop of blood on a test strip to determine blood glucose level. Humans with diabetes often use these devices at home to monitor their own blood sugar readings to provide to their physicians, thus negating the need to stay at a hospital all day for a blood glucose to be performed; their doctors can just use their readings to graph the glucose curve. Many pet owners ask me if they can use glucometers to track their pet’s blood sugar rather than coming into the veterinary clinic. In some circumstances, this can be done. However, before you purchase a glucometer for your pet, a few things must be considered:
Veterinary glucometers are more reliable for the blood glucose measurements of dogs and cats than are human machines. Ask your personal vet for veterinary glucometer brands. One example is by AlphaTRAK®.- Test strip codes cannot be shared among species, i.e. the same test strip coded for humans is different from that of dogs which is different from that of cats. By not programming your glucometer for your pet’s species type prior to sampling, the blood glucose reading will yield a false measurement and be considered invalid. Thus, make sure you’re using an acceptable test strip and the correct code.
- Always ask your veterinarian how to obtain a blood sample and use the glucometer prior to attempting to do so yourself. Some pet owners safely learn to use their pet’s ear tip margin or paw pad as a less-painful sampling site. Always use a new sterile needle or lancet with each use.
- At-home blood glucose readings should never be used by pet owners as a determination of insulin dosage. Do NOT alter your veterinarian’s prescribed insulin instructions based on your pet’s readings. Always consult with your vet before changing your pet’s medications. Otherwise, the results can be deadly.
- At-home monitoring of your pet’s response to his or her diabetic therapy is important, but it does not replace your veterinarian’s expertise. Regular check-ups involving physical exams, more thorough bloodwork, and urinalysis is still required to grant your vet all the tools he or she needs to best treat your dog or cat.
Other aspects of at-home monitoring include keeping a daily log of your pet’s clinical signs (urination, water consumption, appetite) and insulin therapy. A good old-fashioned pen and paper will do the trick, or you may wish to check out the free Pet Diabetes Tracker app on your smartphone.
– Maranda Elswick, DVM
