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September 10, 2001


Question from :

How do most people adjust their insulin? We use a Humalog and NPH mixture in the morning, Humalog at supper, and NPH at bedtime. The Humalog in the morning affects lunch, the NPH in the morning affects supper, the Humalog at supper affects the bedtime sugar, and the NPH affects the morning sugar. Right? How do you figure out how much to adjust each? Is it one unit for Humalog and two units for NPH, or is it a percentage of the total?


There are a number of ways to adjust insulin. Your recollections about how different insulins act optimally at different times are generally true. However, Humalog insulin at breakfast (or dinner) does not really affect the lunchtime and bedtime sugars, respectively. Humalog is really pretty much out of the system three to four hours after you give it. Humalog mostly affects your glucose about two hours or so after you give it, so it mostly just covers the meal you ate. The NPH affects your reading “two readings later” (i.e., the breakfast NPH best influences the suppertime reading and the bedtime NPH best influences the next morning reading).

So how to adjust? If you carb count, then a rule of thumb is that 1 unit of Humalog covers about 15 grams (“1 CARB”) consumed. Some people are more sensitive (and require less insulin) and others less sensitive (thus require more insulin). Depending on a variety of factors, many patients will tolerate “10% changes”, more or less. For example, total the complete daily dose of insulin, take 10% of that, and distribute over the day to cover the higher readings.

These are self-management issues that I bet your diabetes team would be happy to discuss more with you.