Diabetes Mellitus

This is one of the most common endocrine disorders we see in our pet population.  In pets, it is due to a lack of insulin production by the pancreas or a poor response to the insulin they are producing.  Therefore, our pets are usually insulin dependent and generally require for us to supplement them via insulin injections. The cells in their body cannot process sugar so they “think” they are starving, which is why our diabetic pets tend to have a great appetite but lose weight.

For both dogs and cats, obesity is a risk factor. There ARE certain breeds of dogs that have a higher risk: Keeshonds, miniature pinchers, Cairn terriers, poodles, dachsunds, mini schnauzers and beagles. But this is possible IN any breed or mixed breed dog. 

This is generally a problem of older pets (>8yrs of age) though I have absolutely seen it in younger cats and dogs (I can think of several 5 and 6 yr old pets off the top of my head). 

Risk factors that may predispose your pet to this: being overweight and pancreatitis (inflammation of the pancreas). Pancreatitis will be covered another day but tends to occur more chronically (and often under the radar) in cats. Some drugs, like steroids (prednisone, Depo-Medrol injections, dexamethasone) can predispose a pet to DM. 

The primary complaint from the pet owner is that the animal is drinking excessively and urinating excessively, sometimes having accidents in the house/out of the litterbox.   There is also usually some weight loss especially as this goes on longer.

It is easy to test for - in routine bloodwork and a urinalysis. In cats, stress can cause their blood sugar (glucose) level to be high. Stressed cats can have a blood glucose of up to 300 mg/dl and NOT be diabetic.  If we see it above that, we look at the urine and the clinical signs the pet is showing. 

If there is still any uncertainty, we can have the lab run a fructosamine level on the blood. THIS tests for a protein bound portion that is absolutely NOT affected by stress or any one point in time. In fact, it allows us too “view” the past few weeks of a pet’s blood sugar levels as a general average value.   We often use it as a monitoring tool once the pet is on insulin.

Initially, if we find your pet to be diabetic, we will prescribe insulin injections (most often twice a day) and some dietary changes. This is key in cats as they can often AVOID or come off of injections by being put on a high protein diet (sometimes referred to as “CATkins”). There have been cats that have “revereted” to NON diabetic states once they are eating more of a canned food diet. 

Dry foods are great...for pet owners. They are cheaper and keep for a longer period of time. However, they often have a higher amount of carbohydrates in them, which can be a problem for the feline gastrointestinsal system, which is designed for an obligate carnivore (meat eater!). 

As far as insulin types, I won’t go into great depth on this. Why? Well, over the years I’ve been in practice, the insulin available to us as veterinarians changes often. And trust me when I say that working with diabetic pets is truly ART as much as science. 

For dogs, most commonly, we have used NPH, which is a HUMAN recombinent insulin. There have been veterinary formulations, which have come on and off the market. The cats have done the best with PZI (porcine zinc insulin) but 1)this can be difficult to get at times 2) you need to have a reliable source that is consistent in what it is producing. Glargine, a human insulin, has also been used with success in cats, but it is costly. Still, some have found that by starting with glargine and a diet change to a protein based diet, in a few months, they only need the diet. 

Initially, some vets may want to keep your pet in the hospital to see how they do with a given dose of insulin. They will take measurements approximiately every 2 hours. We refer to this as a glucose curve. Not all vets will do this. Some prefer NOT to do it with cats. 

There are some things that can make a diabetic pet difficult to regulate: any sources of infection (including dental disease), being unspayed, other diseases, like Cushing's (tomorrow's topic) and medications (steroids like prednisone).  These need to be dealt with to help your pet do well. 

In dogs more than cats, unregulated diabetes often leads to cataracts. Unregulated animals will also continue to lose weight. We do not tend to see the other problems (like kidney issues and circulatory problems with the feet, etc) that are seen in human diabetic patients. Unregulated or untreated pets can end up in a severely depressed and comatose-like state (known as diabetic ketoacidosis) that requires hospitalization and intensive care with IV fluids and doses of regular insulin to get the blood sugar down. 

It is very easy to teach a pet owner how to give an insulin injection. The needle size we use is smaller than a vaccine needle.  There are different syringes depending on insulin type so do NOT think they are interchangeable. There are U-40 and U-100 insulins out there. 

One quick note about oral hypoglycemics that people use. In my experience, these do not work very well. They can work for a few so it could be worth trying especially in a cat that may be difficult to give a shot to but I've found even in those cases, eventually, it no longer works. 


Your vet and their staff will go over all the details of caring for a diabetic pet. It may seem overwhelming at first, but trust me, many pets owners deal with this quite successfully.  Every pet is different in how they respond.

Yes, you can test at home, especially if you feel comfortable with a little skin prick in the cat or dog’s ear or foot pad. Ask your vet about which monitor to use. There are a few that have been made specifically for animals. 

But do not change doseages without consulting with your vet. Trends are what is important. There can be a tendency to try to too closely tighten where the blood sugar level is and this can cause problems of its own. 

I advise owners to watch the drinking/urinating. This should go down and back to what was considered normal as the pet gets better regulated. Regular rechecks of bloodwork AND weight checks will help us know if the pet is regulated. 

Frequent communication between you and your vet are key to keeping your pet healthy during this time. 

Some key points I REALLY want you to take home:

1. Never ignore changes in your pet’s habits
2. If your animal is diabetic, do NOT give insulin if the pet is NOT eating and please CALL your vet
3. Watch for signs of low blood sugar (wobbliness, seizures) and keep some Karo syrup around for rubbing on the gums, lips, etc. CALL YOUR VET!
4. If your schedule gets thrown off by a few hours, do not give insulin, it’s better for a pet’s sugar to be too high for a short time then to dip too low
5. If you are giving insulin and the pet moves and you aren't sure how much they got, don't try to figure it out. You could give too much. Just do the next dose as usual.
6. Keeping weight OFF your pet is easier than getting it off so start young! This may prevent diabetes all together.