Q:My 11-year-old neutered male has developed diabetes. We’ve been giving insulin twice a day for over a month now, starting out at 1 unit twice daily. Now, we’re up to 5 units twice daily (increased weekly by 1 unit). I monitor his glucose level at least once a day, per my veterinarian’s instructions of usually 6 hours after injection. He registers anywhere from high on the monitor to a low of 412. He has developed neuropathy in all four legs and struggles to get around. The veterinarian says this will go away after we get him regulated.
My questions are:
How much is too much insulin for a 15-lb. cat (he’s still losing weight from a high of almost 18 lbs. to 15.2 lbs. now)?
How long will it take to get him regulated (we’ve been trying to figure it out for a month now)?
Should I try a different insulin (currently using ProZinc)?
A: Thanks for getting in touch, and I am sorry to hear of your cat’s health problems. As you are experiencing, individualizing insulin therapy for cats with diabetes can be challenging in some cases, but perhaps a few points to consider would be helpful. Of course, it is very important that you continue to work carefully with your veterinarian to achieve the best possible outcome.
Determining the ideal dose of insulin for a cat with diabetes ideally involves selecting the type of insulin to be used (intermediate-acting or long-acting; ProZinc is a long-acting formulation), starting at a standard dose (usually 1 to 1.5 units twice daily), starting on a diabetes-friendly diet (low carbohydrate : <12% metabolizable energy (ME) from carbs, moderate to high protein : >40% ME from protein, and low energy density to promote weight loss if needed), and performing a glucose curve, during which blood glucose is monitored over a 12-hour period, one week later. Adjustments to the dose of insulin and, in some cases, the type of insulin used are ideally based upon the results of the glucose curve.
If, for example, the curve shows that the blood glucose does not get low enough after insulin administration, an increase in dose (often in 0.5 U increments) may be required. If the blood glucose gets too low, a decrease in insulin dose may be warranted. If the duration of action of the insulin is either too long or too short, changing formulations of insulin may be necessary.
Another test that can be performed to evaluate long-term glucose control is a serum fructosamine test. Unlike the blood glucose curve, this blood test gives the clinician an idea of how well blood glucose is controlled over a longer period of time (approximately one month prior to sampling).
Different diabetic cats take different amounts of time to achieve good glycemic control, and in many cats, diabetic remission (defined as the point at which a well-controlled diabetic no longer requires insulin) can be achieved. Cats that are overweight have a lower chance of achieving diabetic remission, so carefully managed weight loss is important in diabetic cats that may be carrying a bit too much weight.
In some cases, cats may be resistant to the effects of insulin, and in these cases, control of blood glucose can be challenging. Insulin resistance is usually diagnosed when cats require more than 1 U/kg (unit per kilogram) of insulin twice daily to manage their blood glucose and continue to show signs of diabetes (i.e., increased thirst/urination, weight loss) despite these high doses.
Potential causes of apparent insulin resistance include technical problems (i.e., inappropriate insulin storage, poor injection technique, stress-induced hyperglycemia due to veterinary visit) and those of true insulin resistance include other medical problems like hyperthyroidism, growth hormone excess, the administration of steroids, and various causes of inflammation.
I hope that this brief review of some important topics in feline diabetes is helpful. Please continue to work closely with your veterinarian, and if he/she feels the need for assistance in managing this case, consultation with a veterinary internist can be very helpful.ν