Diabetes in Cats by Frank Utchen, DVM

One of the less common problems we see in cats, yet perhaps the condition requiring the most patience and cooperation between a veterinarian and cat owner, is diabetes.

Yes, diabetes can happen to cats and dogs just as it does in people. One distinct difference is that in cats diabetes can be reversible, and with early treatment and proper diet approximately 1/3 of cats will revert back to an un-diabetic state.

So how do you know your cat may be diabetic? The outward indicators are typically excessive drinking and urinating, with a normal or increased appetite, yet with progressive weight loss. Without adequate insulin the body is unable to properly store fat and weight loss ensues despite normal or increased food intake.

A veterinarian can measure a cat's blood glucose (sugar) or urine glucose level to confirm the presence of diabetes. Blood or urine tests like these are important to distinguish diabetes from other conditions that can cause a similar increase in water intake and urination, and weight loss, such as kidney disease or hyperthyroidism.

The treatment for diabetes involves once- or twice-daily injections of insulin, and feeding an appropriate low-carbohydrate, higher protein diet.  There are several different kinds of insulin available for use, and the type generally recommended for cats is called "Lantus" insulin (also called "Glargine"). These injections are given using insulin syringes with tiny needles, injected in the skin over the back of the neck. The needles are incredibly small and I have yet to encounter a cat who objected to being given insulin injections. Even though many cat owners are intimidated by the prospect of having to give their cat insulin injections, I have never found a cat owner who felt it was difficult after they got started doing it. It really is easy to do.

We start with a low dose of insulin and work our way up to whatever dose a cat requires. If we start with a dose that is too high, we can lower the blood sugar too much, and that is dangerous—a cat can have a seizure if the blood sugar goes too low. Of course, having high blood sugar is not good either, but at least with high blood sugar there is not an immediate risk of a serious problem like a seizure that can happen if the blood sugar drops too low.

Perhaps surprising to most people, it is a simple procedure to measure a cat's blood sugar using the same type of monitor that people use to check their own blood sugar level. A tiny pin prick of the ear is generally ignored by a cat, and allows a small drop of blood to be obtained for home testing. For most people and cats this is much easier (and cheaper) than bringing a cat into the hospital to do it. Most cats require twice-a-day insulin, but a few cats can be managed by just giving it once a day. By measuring a cat's blood sugar every week and adjusting the insulin dose gradually upward until her blood sugar has dropped to normal, we can manage most cases of feline diabetes without complication.

That whole process of determining the correct dose of insulin for a particular cat can take a month or two, so just be prepared for it to seem like a long time before your veterinarian gets the insulin dose figured out exactly. Even then, it's likely that your cat's blood sugar level will not be within the normal range 24/7--diabetes is just too erratic of a disease to get it right every minute of the day. The goals in managing diabetes in cats are these, in this order:

1. Keep their body weight stable or increasing. If this is the case, the dose of insulin is virtually always adequate.
2. Keep their water intake and urine output normal.
3. Keep their blood sugar levels normal.

The blood sugar level jumps around so much, even in human diabetics, that there will be plenty of times during a day when a cat's blood sugar level will be too high. It can be discouraging if you get obsessed with keeping the "numbers" right, because blood sugar levels fluctuate a lot, even in well-managed diabetics.

The diets usually recommended for diabetic cats are low carbohydrate, high protein foods such as "Purina DM" or "Prescription Diet m/d". Amazingly, about 1/3 of the diabetic cats will revert back to normal (i.e., become "un-diabetic" and no longer require insulin shots) if they are given insulin for a few months and eat one of these foods.

Because cats are adapted to eating high protein, low carbohydrate diets in the first place, it is not recommended that diabetic cats continue eating dry foods (with the exception of those specially formulated foods mentioned above). Dry cat foods are often 35% or more carbohydrate, and carbohydrates are metabolized to sugar, which makes diabetes management more difficult. In fact, sugar and carbohydrates in general are so foreign to a cat's system that it was recently discovered that the gene for the presence of the "sweet" taste bud has evolved away in cats and they can no longer detect that flavor in foods.

Diabetes can be a challenging condition to manage in cats. But with patience and dedication it can be one of the most rewarding diseases to treat, and a cat who would otherwise have their life severely foreshortened by diabetes can continue to live a normal and fulfilling feline life.