Diabetes Mellitus in Dogs and Cats
Methods to Diagnose and Monitor Canine and Feline Diabetes
Aug 8, 2009
Diabetes mellitus in dogs and cats is a frequently diagnosed illness and the hallmark feature of the disease is a consistently elevated blood glucose (blood sugar) level. However, diagnosing and monitoring diabetes in both dogs and cats usually requires more than a simple blood glucose test.
Diagnosing Canine and Feline Diabetes
While an elevated blood glucose level is always seen in dogs and cats with untreated diabetes mellitus, a solitary elevated blood glucose level by itself may not be enough to accurately diagnose diabetes mellitus. Animals may have elevated blood glucose levels for other reasons. A stress-induced hyperglycemia (elevated blood glucose level) is common, particularly in cats. Even a trip to the vet can be enough to cause an elevation in blood glucose levels in many cats and this stress hyperglycemia can be difficult to distinguish from a true hyperglycemia.
Clinical signs need to be considered any time blood test results are examined. Typical signs of canine and feline diabetes include increased water consumption, increased urine volume and weight loss.
Fructosamine in Diagnosing and Monitoring Diabetes in Dogs and Cats
Demonstrating persistently high blood glucose levels is necessary to diagnose diabetes mellitus in dogs and cats. Fructosamine is a commonly used blood test which facilitates documentation of persistent hyperglycemia.
Fructosamine is a glycated serum protein complex (a glucose molecule bound to a serum protein) which provides an average reading of the blood glucose level over a period of 10-21 days. Elevated fructosamine levels indicate a persistent hyperglycemia. Therefore, fructosamine is a commonly used confirmatory test for diabetes mellitus in both cats and dogs.
Fructosamine levels can also be used as an aid in monitoring diabetic dogs and cats for their response to treatment. However, it needs to be remembered that, as an average, fructosamine levels do not provide any information about how high or how low individual blood glucose levels may swing. This can become especially important in evaluating whether an individual pet's response to insulin may place the pet in danger of a hypoglycemic crisis, where the blood glucose falls to a dangerously low level.
Glycosylated hemoglobin and glycosylated albumin are similar to fructosamine measurements in that they measure the average blood glucose concentration over an extended period of time. However, they are less frequently used for diagnosing and/or monitoring diabetes.
Blood Glucose Curves in Diabetic Dogs and Cats
Blood glucose curves are useful in evaluating the efficacy of insulin treatment and can be used to determine:
- whether insulin is being absorbed properly
- how long the insulin takes to begin working (the onset of action)
- how long the insulin takes to reach its peak activity
- how low the blood glucose level falls when the insulin is at its peak activity (the blood glucose nadir)
- how long the insulin has effect in the diabetic animal (the duration of effect)
- how far apart the blood glucose levels are between the highest and lowest readings (the glucose delta)
The ideal insulin dosage maintains the blood glucose levels between 80-200 mg/dL in dogs and 80-300 mg/dL in cats, with a glucose nadir between 80-150 mg/dL. Glucose nadirs less than 80 mg/dL may predispose the pet to developing hypoglycemia, which may become life-threatening.
The duration of effect aids in determining how often the insulin must be administered. Most pets require dosage every 12 hours.
Monitoring Urine in Diabetic Dogs and Cats
Urine may also be monitored for both glucose and ketone values. Dip sticks are available in most pharmacies which allow the measurement of both glucose and ketone levels in the urine. Insulin dosages generally are not changed based on urine glucose readings, but persistently high urine glucose values may indicate the need for further evaluation of the pet's condition.
Urine ketone levels can also be monitored easily at home. Occasionally, ketones will be detected in the urine and this is normal. However, if ketone levels persist for longer than 3 days, an immediate visit to the veterinarian for further evaluation is in order.
Various methods are available to diagnose and monitor diabetic dogs and cats, but fructosamine is the best method for confirming a diagnosis, assuming the pet also shows clinical signs of diabetes and displays hyperglycemia. Fructosamine and blood glucose curves are probably the two most valuable tools for monitoring diabetic dogs and cats. Devices which feature probes which are placed under the skin for the purpose of continuously measuring glucose are also now available and may eventually provide an additional commonly used method of monitoring diabetes in dogs and cats.
Sources:
Monitoring Diabetic Dogs, Part 1: Blood Glucose Curves, Keven P. Gulikers, William E. Monroe, Veterinary Medicine December 2003;98(12):1025-1031.
Monitoring Diabetic Dogs, Part 2: Fructosamine and Glycosylated Hemoglobin Concentrations, Keven P. Gulikers, William E. Monroe, Veterinary Medicine December 2003;98(12):1034-1036.
Monitoring Insulin Therapy, Margi Sirois, American College of Internal Medicine Proceedings, 2003.
Continuous glucose monitoring in dogs and cats, C E Wiedmeyer, A E Declue, Journal of Veterinary Internal Medicine 2008 Jan-Feb;22(1):2-8.
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