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Short-Acting Insulin Isn’t Short for Most Type 2s

If you forgot to test, you’re in good company. It seems that the scientific researchers whom you rely on for your professional guidance on diabetes made the same mistake.

When they tested the short-acting insulins, they forgot that the great majority of us with type 2 diabetes carry around too much weight. This awful report just came out in a late-breaking abstract presented at the American Diabetes Association’s scientific sessions in Chicago. Dr. Jean L. Ardilouze, a professor of medicine at University of Sherbrooke in Quebec, Canada, and three colleagues presented “In Obese Subjects with Type 2 Diabetes, Are Short Acting Insulin Analogues That Short?”

Their conclusion was this:

In healthy normal weight subjects, our results reproduced data accepted and used in daily practice for insulin prescriptions. However, in a population of obese subjects with type 2 diabetes, we show for the first time that plasma levels of short-acting insulins are blunted, at low dosage, and severely delayed at average dosage. Our data therefore question the timing of injection and the effectiveness of short acting insulins in obese subjects with type 2 diabetes, so commonly treated by general practitioners and endocrinologists.

We are talking here about some of the most commonly used insulins on the market – Humalog, Novalog, and Apidra. Humalog is lispro, which Dr. Ardilouze mentioned by name in his report, although we usually identify it (and Novalog and Apidra) as a rapid-acting insulin (onset less than 15 minutes). What we know here as short-acting insulins, like Humulin and Novolin, act in half an hour to two hours.

So there’s some confusion about the terminology here. But you shouldn’t have any confusion about the facts.

Dr. Ardilouze says that his biggest surprise when he started his research was discovering that scientists hadn’t studied these insulins in obese people with type 2 diabetes. They had been studied only in young, lean people with type 1 diabetes, he says. He says that one product, which he didn’t identify, says “in tiny writing on the label” that they hadn’t studied it in obese people with type 2 diabetes.

He must be referring to Novolog (aspart). I don’t have ready access to the labels, but Novo Nordisk’s prescribing information for it says, “Pharmacokinetic/pharmacodynamic characteristics of insulin aspart have not been established in patients with Type 2 diabetes.” However, Lilly’s prescribing information for Humalog does say that they studied it in two groups of 25 and 722 type 2s. Still, it doesn’t say anything about their weight. And the Sanofi-Aventis prescribing information for Apidra says they did study it in 18 “obese, non-diabetic subjects,” although they don’t say anything about the amount of insulin they took.

Dr. Ardilouze studies the biology of fat tissue. When he learned that fat tissue restricts blood flow, he wondered about the implications of weight for people who take insulin, who generally use more insulin than thin type 1s. He discovered that the bigger the dose, the longer it takes the insulin to work.

“If you inject 10 units of short-acting insulin into obese subjects, there is not much difference in time to peak effect,” he said. “But the time is tripled with triple the dose – the kind of dose an obese person with diabetes is much more likely to need.”

This means that what we generally call rapid-acting insulin isn’t rapid at all. It may take as much as 45 minutes to go to work.

This could explain a lot of the control issues that I’ve seen among type 2s who use Humalog or Novolog. I know obese type 2s who take rapid-acting insulin immediately before eating and then wondered why the insulin didn’t match their food intake.

If you take large doses of one of the rapid-acting insulins and are seeing a mismatch, what can you do now? Certainly a few days of careful testing of your blood glucose levels before and after your meals at half-hour intervals will help. If you find that your glucose and insulin peaks aren’t matching well enough, you can discuss with your physician or diabetes nurse educator about injecting sooner – half an hour to 45 minutes before eating might work better.

This article is based on an earlier version of my article published by HealthCentral.

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