Diabetes Mellitus in Dogs and Cats

What is diabetes mellitus?

Diabetes mellitus is a condition that occurs due to insulin deficiency within the body. The name is derived from the Greek words “diabetes,” meaning excessive urination and the Latin word “mellitus” referring to honey or the presence of sugar. When a patient’s blood sugar is high, sugar will “spill over” into the urine. Water is also pulled into the urine resulting in excessive urination, hence the name diabetes mellitus.

Similar to in people, diabetes mellitus in dogs and cats occurs in two forms, Type 1 diabetes and Type 2 diabetes. 

Type 1 diabetes

• The most common type recognized in dogs and cats
• Develops due to destruction or damage to the cells in the pancreas that produce insulin and requires life-long insulin injections

Type 2 diabetes

• Occurs occasionally in cats and rarely in dogs. 
• Usually associated with insulin resistance within the body 
• Commonly seen in obese or overweight animals or can occur secondary to hormonal disorders 
• If Type 2 diabetes is treated early, administration of insulin may only be intermittent or not required in rare cases

What are signs that my pet has diabetes mellitus?

Increased water consumption and urination are the two most common signs seen in diabetic dogs and cats. Dogs and cats with diabetes often have a good appetite but tend to lose weight. Dogs with diabetes often develop cataracts in their eyes causing vision problems or blindness. The diabetic cataracts can be treated surgically by a veterinary ophthalmologist. Diabetic cats may develop weakness in their back legs and walk with their heels on the ground (called plantigrade stance); this may or may not be reversible with treatment.

Additional signs of illness (vomiting, diarrhea, or decreased appetite) may be seen in diabetic pets that are left untreated or in those that develop concurrent illness that complicates the control of their disease. This requires immediate evaluation by a veterinarian. 

How is diabetes diagnosed in dogs and cats?

Diabetes mellitus is diagnosed by the presence of elevated blood glucose (sugar) and glucose in the urine. Unfortunately, stress can cause elevation in blood glucose and glucose in the urine of cats, which may make the diagnosis more challenging. Additional tests may be recommended to confirm the diagnosis of diabetes mellitus. The fructosamine test is a simple blood test that gives the veterinarian the pet’s average blood sugar level over the previous 1-2 weeks and may be used by veterinarians to help diagnose diabetes.   

After diagnosis of diabetes, your veterinarian may recommend additional tests to screen for other conditions commonly seen with diabetes mellitus. 

What is the treatment?

Treatment of diabetes requires, in most cases, the administration of daily insulin injections. Other treatments may include the following: 

• A change in diet (especially important for cats)
• Exercise to promote weight loss and/or to maintain an ideal body weight
• Oral medications to lower blood sugar

The exact treatment recommendations, including the type and dose of insulin, vary by case and should be determined by your pet’s veterinarian. Insulin needs can be quite variable, so different insulin types, doses and even frequencies may be attempted until your dog or cat’s disease becomes controlled. Insulin handling, storage and administration (including the type of insulin syringe) is different for each insulin type and should be reviewed with your veterinarian. In a majority of cases, dogs with diabetes require life-long daily insulin injections. If treated early and with management of obesity, some cats with diabetes can go into remission after diagnosis. In mild cases, insulin use may be avoided altogether (managed with diet and weight loss) or only needed temporarily. 

Once an animal is started on treatment, regular visits to your veterinarian are needed to evaluate diabetic control and to identify and treat concurrent disease that may cause insulin resistance. Ultimately, the goal in treating most animals with diabetes is to minimize clinical signs and maintain body weight, since “curing” the disease is generally not possible, especially in dogs.

What is the prognosis?

Overall prognosis for an animal with diabetes mellitus is good. Many of these animals are able to live long healthy lives with appropriate veterinary care and dedicated owner commitment. Treatments for diabetes mellitus might initially appear overwhelming, but with time can become part of you and your pet’s daily routine.

Edited By:
Stacie Summers, DVM, DACVIM (SAIM)