Understanding Diabetes

To better understand what happens with diabetes mellitus, let’s start with reviewing the body's normal sugar metabolism:

The cells of the body require fuel in the form of fat or sugar. Glucose comes from the diet in the form of starches and sugars that we eat. Cells cannot absorb glucose unless a hormone known as insulin is present, which is produced by the pancreas. Insulin is like a key that unlocks the door, allowing sugar in the bloodstream to enter the body’s cells. Once inside the tissues, glucose can be burned for fuel or stored, but without insulin, the sugar stays in the bloodstream and cannot be used by the body.

With no insulin (as in a diabetic animal), glucose cannot get into the cells to be utilized. The body's tissues are starving and the bloodstream has plenty of glucose to feed them, but without insulin, the glucose is unavailable.

What symptoms are present in a diabetic animal?

Diagnosing diabetes is fairly straight-forward. Often, we will catch it on routine bloodwork- blood glucose levels are typically extremely high in unregulated diabetic patients. Normally, the kidney is able to conserve the bloodstream's glucose but with diabetes, they are flooded with glucose and the excess spills over into the urine. Glucose is able to draw water with it, which translates into excessive thirst and excessive urination for a diabetic patient.

In a diabetic patient, the tissues of the body are unable to access any of the glucose they need for fuel and are basically starving. Fat is mobilized and muscle is broken down to help feed the tissues but it does not do much good without insulin to bring fuel inside the cells. The patient shows excessive appetite because his body is in a state of starvation. Because the body is rapidly breaking itself down, weight loss is also a classic sign of diabetes.

Side note: All the sugar in the urine provides a desirable growth medium for bacteria and urinary tract infection is a common finding in diabetes mellitus. 

Are Insulin shots required?

Dogs typically develop insulin-dependent diabetes (similar to Type I, or juvenile onset in humans) and must be treated with insulin. There is no way around it. 

Most cats have non-insulin dependent diabetes, which has many similarities to Type II diabetes in people. The term "non-insulin dependent" might suggest that cats can get away without insulin injections, but that is not the case. In cats, there is a possibility of diabetes resolving (if the pancreas improves its insulin-secreting ability). In order to have a chance at this happening, insulin injections are definitely needed at least in the beginning.  


There are some diets and feeding recommendations that are helpful to regulate diabetes. The high protein/low carbohydrate/high fiber diets seem to be the most beneficial. There are specific prescription diets, both canned and dry, available for diabetic patients. 

How do we monitor diabetic patients? 

Your pet is going to periodically need a blood glucose curve to be sure the amount of insulin being given is appropriate. This involves checking the glucose about every 2 hours. This is done anytime the dose of insulin is changed, or if anything new is happening with your pet (such as unexpected weight loss, vomiting, or changes in thirst/urination). 

I also like to encourage owners to try to get in the habit of checking a blood glucose once to twice a day- if this is possible, your veterinarian can make a sliding insulin scale (tailored to your pet) based on what the blood glucose readings are. This is a much better way to achieve tighter regulation, and is very similar to how people regulate their diabetes on a day to day basis. It’s really not as difficult as it sounds!


The most serious problem to watch for is hypoglycemia (low blood sugar). If an insulin dose is too high, or your pet doesn’t eat, hypoglycemia is likely to result.  Your pet may look tired, weak, or possibly wobbly/drunk. This can be an emergency and can progress to seizures. If low blood sugar is suspected, first try to get your pet to eat. If no interest in food, rub Karo syrup, honey, or pancake syrup on the gums. The sugar will absorb directly from the mouth, swallowing is not necessary. Next, seek veterinary care immediately. 

To Review:

The main symptoms of diabetes mellitus are:

  • Excessive thirst

  • Excessive urination

  • Weight loss (especially in the face of an increased appetite)

If you feel like your pet could be diabetic, please reach out to your veterinarian to have them checked!