Diabetes Mellitus (Sugar Diabetes) - Testing and Monitoring Dogs and Cats

Diabetes mellitus (DM or sugar diabetes) is often a disease of overweight, middle aged animals. The classical signs are weight loss, increased appetite, increased thirst and increased urination. It is usually first diagnosed by the clinical signs together with a simple urine test similar to that carried out in humans. Once a provisional diagnosis has been made, a definitive diagnosis will depend upon further tests.

What are these tests?

Tests usually involve a complete blood count (CBC) which includes white cells, red cells and platelets, a serum biochemistry profile and a full urine analysis.

If the condition is suspected as a result of the signs of weight loss, with increased appetite, thirst and urination, why cannot the condition be confirmed just on blood sugar and the presence of sugar in the urine?

Fasting blood and urine results with elevated glucose levels are essential for the diagnosis of Diabetes mellitus. Further screening tests often give us additional information regarding the animal's general condition and may give further information on life complicating conditions which may influence the line of treatment. For example, diabetic animals are more prone to infections as a result of the diabetes and the CBC often will give an early indication of the problem.

Is it really necessary to do so many serum biochemistry tests?

Serum, which is the liquid portion of the blood, contains many substances including glucose, enzymes, fats, proteins and carbohydrates together with metabolic waste products. The determination of the serum glucose level plays a major role in the definitive diagnosis of DM. However this does have some problems.

Cats, and to a lesser extent, some dogs, can present a challenge because serum glucose concentrations can be raised significantly simply due to the stress of being at the vets and having a blood sample taken. In addition, blood glucose is also mildly elevated for several hours following a meal. Therefore confirmation of diabetes may require several blood samples collected over a period several days.

I have heard that fructosamine tests are more accurate. Can they be done? 

Yes. Diabetes may be diagnosed by an elevated serum fructosamine result. Fructosamine is formed as a result of the binding of glucose with certain proteins in the blood stream. The higher the blood glucose, the greater the amount of fructosamine formed. Fructosamine can be measured from a single blood sample. Unlike glucose, it is not affected by the stress level of the animal. It is an extremely useful test and acts as an indicator of the average blood glucose concentration over the previous two to three weeks. It is particularly useful in long term monitoring of diabetic pets. 

Why then has it not replaced these repeated glucose estimations?

The fructosamine result should be regarded as a retrospective assessment of the average blood glucose concentration over the last two to three weeks. It will reliably indicate that elevated blood glucose levels have been present for at least fourteen days prior to the estimation. It also gives an indication of how well stabilised the pet is, once treatment with insulin is under way. However it does not detect recent fluctuations in blood glucose concentrations. Therefore it cannot be used to calculate any changes in daily insulin dosage. For this reason, a daily blood glucose estimation is usually still required to “fine tune” the required insulin dose. 

What about urine tests, are they not important?

Prior to the development of simple, accurate blood glucose tests, both for us and our pets, daily insulin estimation depended upon the amount of glucose in the urine. It is still a very important test.

What is involved?

The test is very simple once the patient has been persuaded to allow you to obtain the urine sample! Remember the container should always be very clean to ensure the results are accurate. Dogs are usually more cooperative than cats although today there are special cat litters available that allow acceptable urine samples to be collected. All that is then necessary is to dip a urine test strip in the sample and after a specified time to read the result.

Does urine glucose have to be tested every day?

At the beginning of insulin therapy at least daily monitoring of urine glucose is indicated. We will advise regarding this once the optimal insulin dosage has been determined and diet and exercise has been stabilised. Monitoring may then involve urine testing only once or twice a week.

What other indicators are there to indicate that my pet is reasonably stabilised on the insulin dose?

Monitoring appetite, weight, water consumption, urine output and energy levels are probably just as important as urine tests. With cats in particular obtaining a urine sample can present problems. Many owners depend upon careful monitoring of fluid intake and weight combined with changes in demeanour, etc. It is important that if you note any increase in thirst, however slight, we are advised.

Are there any other routine tests that will be necessary?

Serum biochemistry tests involve not only evaluation of glucose levels but include tests that give an indication regarding liver and kidney function. Results can range from mild elevation of liver enzymes due to dehydration (as a result of the previously undetected diabetes) to more severe liver damage due to alterations in fat metabolism. The latter may also be reflected in elevated serum cholesterol levels.

Will these tests have to be repeated for the rest of my pet's life?

At present, treatment for diabetes involves stabilising but not curing the patient. Daily injections of insulin are usually required for the rest of the pet's life although rarely spontaneous recovery can occur. In cats particularly, a temporary recovery (called remission) can sometimes occur. Once exercise levels, food and insulin dosage have all been stabilised it is prudent to have regular check-ups, including laboratory tests, in order to ensure that everything is proceeding according to plan.