Diabetes in Dogs
- Mary Malucci
- Jan 28, 2025
- 7 min read
Diabetes in Dogs
Regardless of the species, diabetes mellitus is defined as the body’s inability to regulate glucose in the blood because of a deficiency of insulin. Insulin controls the delivery of glucose into the tissues of the body.
As outlined in my article “Diabetes in Cats”, diabetes is further subdivided into three types, based on the specific cause of the insulin deficiency. In cats, Type II diabetes is more prevalent. In Dogs, Type I diabetes is the most common. Also called insulin dependent diabetes, the beta cells in these dogs are no longer producing insulin. The two most common reasons for this are immune-mediated destruction of the pancreas or severe recurrent pancreatitis. Either way, the dog’s beta cells have been destroyed. These dogs will need to receive insulin injections for the rest of their lives.
The earliest signs of diabetes are increased thirst (polydipsia), increased urination (polyuria), increased appetite and, despite eating well, weight loss. Owners may notice refilling the water bowl more frequently or taking the dog outside more often to urinate. Some dogs who have been well house trained suddenly start urinating in the house. These signs are all related to the excessively high amounts of glucose circulating in the blood (hyperglycemia).
If the hyperglycemia persists long enough, the dog may develop diabetic ketoacidosis (DKA), which is life-threatening. In DKA, the dog’s body has started to break down fats as an alternative fuel source, producing ketones. The ketones affect the dog’s pH balance and electrolyte balance. Ketones change the pH to an acidic state (acidosis), disrupting the fluid distribution in the body. Electrolyte imbalances can lead to abnormal heart rhythms and abnormal muscle function. Dogs in DKA will be weak or lethargic and dehydrated. Their once healthy appetite has disappeared and they may be vomiting.
Your veterinarian will diagnose diabetes based on your dog’s symptoms and history and confirm it with blood work and urinalysis. In the earlier stages, the blood work will show excessive levels of glucose in the blood and urine. It may also give indications of other diseases that may be happening at the same time. For reasons unknown, dogs with high levels of phosphate in their blood when diagnosed have a less positive prognosis. Dogs with a history of pancreatitis, hyperadrenocorticism (Cushing’s disease) or hypothyroidism are more likely to develop diabetes. Female dogs appear to be twice as likely as male dogs to develop diabetes. Other risk factors include age (over 10 years), obesity, and long term steroid use.
Dogs experiencing DKA will show elevated levels of ketones in their blood and urine in addition to excessive glucose. These dogs will need to be hospitalized, often for several days, to treat the PH and electrolyte imbalances and start insulin therapy.
Because the majority of canine diabetics are Type I insulin dependent, injectable insulin is the only available therapy. Oral medications are not applicable to Type I diabetes. There are many types of insulin available and your veterinarian will decide which form is best for your dog. Insulin must be delivered with the appropriate insulin syringe. For instance, NPH insulin is a commonly used form for dogs. The concentration is 100 units of insulin per 1 ml or U100. Thus it is essential that U100 insulin syringes are used to measure and deliver the insulin to your dog.
Insulin injections are usually given twice a day 12 hours apart, ideally at the same times every day. Their meals should be timed to coincide with the insulin. Insulin requires special handling. It must be refrigerated between doses. Some insulins settle and you will see white stuff on the bottom of the bottle. Hold the bottle between your hands and gently roll it to mix. Insulin syringes are marked in units to make it easier to pull up the right dose. The injection is given under the skin. The needles on insulin syringes are tiny and most dogs tolerate them well. Have your veterinarian demonstrate all this.
Nutrition is an important part of managing your diabetic dog. An appropriate diet will be high in fiber to slow sugar absorption and low fat to avoid obesity. There are prescription diets available that address these concerns. Your veterinarian will likely make suggestions. Once you and your dog decide which food you like, it’s important to feed the same food at the same times every day. Avoid high carbohydrate treats like Milk-Bones or other baked treats. Offer your diabetic dog green beans or other vegetables as treats. However, onions and garlic need to be avoided as they are toxic to dogs. Most fruits are primarily sugar so it’s best to avoid them, especially grapes and raisins which are also toxic to dogs.
Exercise is also important to successfully manage your diabetic dog. Many dogs are overweight at diagnosis. Dogs who maintain a consistent healthy weight are more readily regulated on insulin. Exercise makes muscle cells more sensitive to insulin, allowing them to absorb more glucose from the bloodstream during and after activity without requiring high levels of insulin.When muscles contract during activity, muscle cells are able to take up glucose and use it for energy whether insulin is available or not. In this way, exercise helps lower blood sugar levels and enhance insulin sensitivity.
A newly diagnosed diabetic dog will require more frequent monitoring until an appropriate maintenance dose is determined, usually given 12 hours apart. Once that maintenance dose is determined, it’s important not to adjust it without consulting your veterinarian. Over time, a dog may need to have the dose or type of insulin used adjusted to maintain the desired regulation of blood sugar levels.
Historically, blood glucose curves were the best way to know if your dog was responding well to the insulin type and dose. They usually require a day in the hospital, during which the treatment team draws a tiny amount of blood from your dog every two hours and measures the blood glucose. The trend they are looking for is a curve, with the highest values occurring at the times insulin is due and the lowest values seen at the halfway point between insulin doses. The drawback to this approach is the stress of being in the clinic can falsely elevate a dog’s glucose levels.
Some owners have learned to monitor their dog’s glucose at home with the AlphaTrak blood glucose meter. These are designed to be used on dogs and cats and are more accurate than blood glucose meters for humans. The owner must get comfortable pricking the dog’s ear for the required drop of blood needed by the meter. When the owner is comfortable with a procedure, the dog is more relaxed and the blood glucose readings are more accurate.
Another device being used more frequently in dogs is the Freestyle Libre continuous glucose monitoring system. Once the device is properly placed on the dog, the owner can use the reader or even an app on their phone to monitor the blood glucose as often as necessary. I see this used more and more frequently in the ER setting, The devices usually need 12 hours to calibrate to the patient. Since many of these pets are hospitalized for 48 hours or more, the device is placed in the hospital. The calibration is monitored by comparing the blood glucose values from the Freestyle Libre to blood drawn elsewhere from the dog and measured on an AlphaTrak.
To get a feel for a dog’s average blood glucose over the previous week, we can test the blood for fructosamine. Fructosamine tests measure how much sugar is added to albumin and reflects blood glucose over about five days. This alternative can be helpful for pets too anxious or fractious for the traditional blood glucose curve approach.
Monitoring your dog also means being familiar with your dog’s normal behaviors so you can recognize changes that may be important. One of the most dangerous complications of diabetes is hypoglycemia or very low blood sugar. The first sign of this is abnormal behavior, like changes in their mental state such as confusion. The brain is very glucose dependent so the hypoglycemic dog may be lethargic, sleeping more than usual or resisting activity. Severe hypoglycemia is life threatening and can come on very quickly! If the blood sugar drops too low, the dog may have tremors or seizures or collapse into a coma.
In the earlier stages of hypoglycemia, the owner can rub honey or Karo syrup on the dog’s gums and offer some food. If your dog is willing to eat, try offering a meal of cooked pasta with syrup or honey to quickly raise their blood sugar. If you have a way to measure the blood glucose at home, get a reading and call your veterinarian or the ER for advice.
If your dog has progressed to tremors, seizures or coma, get her to the veterinary ER as soon as possible! Be careful trying to rub honey or Karo syrup on the gums of a trembling or seizing pet as these dogs may inadvertently bite.
Hypoglycemia is often the result of a dog receiving insulin despite not eating well. It’s very important that your dog eats her normal meal before getting her dose of insulin because insulin without food will push the blood glucose too low. If your dog refuses to eat or only eats a bite or two, it’s better to skip a dose of insulin than risk hypoglycemia. A diabetic dog can usually miss one dose of insulin without consequence. If your dog is still refusing to eat at the next mealtime, reach out to your veterinarian or the ER for advice.
The other common side effect of diabetes in dogs are cataracts in the eyes, even in dogs who are well regulated. These cataracts tend to mature quickly and will impair your dog’s ability to see. If you see any changes in the color or clarity of your dog’s eyes, seek veterinary care as soon as possible. Your veterinarian may suggest a referral to a veterinary ophthalmologist for the best treatment options.
Managing the diabetic dog requires an owner who is committed to a consistent routine of feedings and insulin administration. The owner needs to be comfortable handling insulin and syringes and giving subcutaneous (under the skin) injections. The owner may want to invest in an AlphaTrak blood glucose meter and get comfortable using it. I usually recommend to owners of newly diagnosed diabetic dogs that they keep a daily log that includes the following information:
insulin type, dose and administration schedule
Meal schedule, type of food given and how well the dog ate
Any changes in behavior or appetite
Exercise routines
Notes about topics to discuss with the veterinarian at the next appointment.
Dogs with diabetes will need to receive insulin injections for the rest of their lives. Committed and diligent owners, in partnership with their veterinarian, can provide full active lives for their diabetic dogs by monitoring closely and seeking veterinary advice as needed.
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