• Robert Skidmore, DVM

Diabetes Mellitus

Diabetes Mellitus is a disease in which the pancreas does not produce insulin in sufficient quantities, if at all, to allow cells of the body to absorb glucose (sugar) and keep blood glucose levels in a specific range. Insulin is produced by pancreatic cells and secreted into the blood stream. Insulin is like the key that enables cells to absorb glucose for fuel. Without insulin blood glucose levels rise, causing symptoms of disease. The body is fooled into thinking it is starving and starts to mobilize fat, starch and protein for glucose. This causes blood glucose to go up even further.

Clinical Signs/Symptoms

Excessive thirst and urination -- kidneys normally prevent glucose loss in the urine. But glucose levels consistently high overwhelm the kidneys and glucose spills over into the urine. Glucose is also able to draw water with it into the urine. This excess urine production leads to increased thirst to keep up with the fluid loss.

Excessive appetite

Weight loss

Disease Forms

Dogs: Virtually all dogs have insulin dependent diabetes, meaning they require insulin injections (usually twice per day).

Cats: Cats also usually require insulin injections, but it’s not unusual for the pancreas to recover weeks or months after starting insulin injections (called a remission). This phenomenon does not typically occur in dogs.


Diagnosis is easily made by checking blood glucose, either by a hand-held glucometer or a full lab panel. If glucose is found in the urine, blood glucose should then be checked.


The goal of treatment is the absence of clinical signs and complications, not necessarily keeping blood glucose in the normal range of 70-125. Most patients will do very well if blood glucose levels are <200 for the majority of the day. When a patient is first diagnosed, the veterinarian will determine a starting dose for insulin and do a glucose curve in the clinic. This involves taking glucose measurements every couple of hours or so to see what the patient’s glucose is doing throughout the day. Then the dose of insulin is adjusted if levels are too high. There are several different types of insulin and your veterinarian will choose one that he or she feels is best for your pet. Glucose curves need to be repeated periodically (every 3 months or so) to make sure the pet is staying in a good range.

Diet is also a tool used in the treatment of diabetes. Historically, high fiber and low carbohydrate diets have been recommended. However, if finances preclude prescription diets, use a good quality food and be consistent with it.

Home Monitoring

Glucose curves can be performed at home thereby saving money on vet visits. This is especially beneficial in cats who are prone to stress hyperglycemia, which gives in inaccurate picture of the glucose curve throughout the day. Use a glucometer specifically for pets since they are calibrated differently from humans. One of the best is the Alphatrak 2, available at chewy.com and other places. Your veterinarian can show you how to use the lancet and there are also several YouTube videos going over the technique. The procedure is as follows: get glucose measurements before the morning meal, feed the pet and give the insulin, take glucose readings every 2-3 hours for the next 12 hours. Send your results to your veterinarian who will then make any necessary adjustments in the insulin dose.

Potential Complications

Diabetic ketoacidosis (DKA): this is a serious and potentially life threatening complication resulting from poor glucose control. This can occur when blood glucose levels are very high for an extended period of time. It results from the rapid breakdown of fats and starches for energy which overwhelms the liver and can result in acute liver failure and other organ and electrolyte abnormalities. If your diabetic pet skips more than 1 meal, is lethargic and not drinking water, get them to your veterinarian as soon as possible for treatment.

Hypoglycemia (low blood sugar): this can occur when the insulin dose is too much causing low blood glucose. It can also occur if insulin is given but the pet does not eat. To help avoid this, give the insulin injection while the pet is eating or just after finishing the meal. Misreading the syringe and giving the wrong dose of insulin can also result in hypoglycemia. Signs of low blood sugar include weakness, lethargy, non-responsiveness and seizures. If you suspect hypoglycemia, rub some pancake syrup on the pet’s gums. Once the pet is more alert (usually within 5-10 minutes), feed him/her. If the pet does not perk up, seek immediate veterinary care.

Cataracts: This is a common complication and can occur even in well regulated dogs. Cataracts typically form very quickly once it starts and the dog can become blind within a month or two. There is surgery available by veterinary ophthalmologists to remove the cataracts which restores vision.

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