About glucose curves
The glucose curve is a great tool to differentiate between an insufficient insulin dose and the Somogyi effect. It helps to determine insulin effectiveness and the maximum and minimum levels of glycemia, which ideally should be between 120–300 mg/dL (5.6–16.7mmol/L) for cats for most of the day.8 Try our online glucose curve generator.
Veterinarians commonly adjust the insulin dose based on a blood glucose curve. When creating a glucose curve, remember that stress can affect the reliability of results, and the glucose curve is only one tool among others that can help diagnose and monitor diabetes mellitus. Take clinical signs (or lack thereof) into account when contemplating any change in the insulin therapy. The ultimate goal in regulating the diabetic cat is to control the clinical signs adequately so that the patient enjoys a good quality of life.
How to complete a glucose curve
The procedure is as follows: shortly after the animal has been given its first meal (preferably at home), the first blood sample is taken just prior to the insulin injection in the morning. Thereafter, blood samples are collected every 2 hours throughout the day for 12 hours, if possible. These data are then plotted on a graph to generate a curve. Veterinarians can determine based on the nadir whether the dose needs to be increased or decreased (or remain as is).
How to interpret a glucose curve
The aim of treatment is to alleviate clinical signs of diabetes. To achieve this goal, keep blood glucose concentrations below the renal threshold and avoid hypoglycemia. Thus, the goal is to maintain blood glucose concentrations roughly between 120 to 300 mg/dL in cats for the majority of the day.8
The duration of insulin action is measured from the time of Vetsulin® (porcine insulin zinc suspension) injection, followed by a fall in blood glucose concentration, to the time that blood glucose exceeds the renal threshold concentration of 200 to 280 mg/dL in cats. Because the added factor of stress can falsely increase the blood glucose values, the goal is to keep the blood glucose between 120 and 300 mg/dL for the majority of the day in cats. For twice-daily Vetsulin treatment to be effective, the duration of insulin activity following each injection needs to reach 10 to 12 hours.
Measuring blood glucose
Blood samples can be taken to measure blood glucose or blood insulin concentrations. Two methods of taking blood samples to produce glucose curves include:
- Collect a venous blood sample from a peripheral vein. Plasma glucose concentrations are measured in the laboratory—the gold standard—or by an in-clinic analyzer.
- Collect a drop of capillary blood from the pinna and analyze it using a handheld glucometer.
- Glucometers should be calibrated specifically for dogs and cats because of the difference in the ratios of glucose in plasma and red blood cells from humans.
- Readings may vary as much as 15% from samples submitted to the laboratory.
- Handheld meters are reasonably accurate. If a reading seems unusual or does not match the clinical signs, a second reading should be taken or another method used to confirm the blood glucose measurement.
Goals of management
Consider treatment successful when the clinical signs of diabetes mellitus improve without inducing hypoglycemia.
After the cat stabilizes successfully, perform routine rechecks every 2 to 4 months. Careful monitoring and control during maintenance will help to limit the long-term complications.
Blood glucose concentrations
The aim of therapy is not to produce a series of blood glucose concentrations that are within the reference range, but to produce a blood glucose curve that approaches the reference range and avoids potentially fatal hypoglycemia. A stable diabetic cat exhibits a blood glucose range of around 120 to 300 mg/dL for most of a 24-hour period. The graph below demonstrates an ideal blood glucose curve for a cat receiving Vetsulin twice daily.
Ideal feline blood glucose curve
Not all blood glucose curves will be ideal at first. For examples of additional blood glucose curve results, please select one of the following: