We recently took our five-year-old daughter, diagnosed three months ago with type 1, to a different endocrinologist because we weren’t comfortable with the one to whom we had been referred. The new endocrinologist told us the Humalog she takes at meals, via injections, stays in her system for four hours. The old endocrine team said it’s gone after two hours and that her sugar won’t go lower after two hours. So, we’re really confused about how long Humalog stays in the system and whether a blood test two hours after a meal, especially dinner/before bed, is really an accurate test.

Unfortunately, there is some variability of how insulin works, how long it lasts, when it peaks, etc. Humalog, Apidra and NovoLog are the rapid acting insulins and they usually start to work about 15 to 30 minutes after being injected. Therefore, the ideal is to provide such insulins about 15 minutes ahead of food. Peak usually is one to two hours and the duration of effect is about three to four hours.

Lantus and Levemir are much longer acting insulins and somewhat more predictable but still have some day-to-day variability. Usually, there is a modest peak about eight to 12 hours after injection. In large doses, it may last 24 hours. For most kids using smaller doses, it usually does not last 24 hours so they often need twice-a-day dosing, but there are some exceptions. Again, dose adjustments should be done based upon blood glucose monitoring results and not dogma/rules.

NPH is an intermediate acting insulin not used so often any longer in most intensified insulin regimens. It is somewhat more variable but onset is about three to four hours, peak is about six to eight hours and it has waning effects by eight to 12 hours. Many of us used to use it in overlapping fashion three or four times a day and most of us have changed to Lantus or Levemir as our basal insulins when insulin pumps are not being used.

But, these are all estimates and one needs to do some before and after meal blood glucose testing to see what works for any individual patient. Probably both doctors were somewhat oversimplifying the peaks and duration data from what you have written. It would be good to go back and have a more detailed discussion at the same time that you provide four or five days of more intensified monitoring results to see what actually works for your own child.

SB