I know that there is a difference in opinions from the experts about the appropriate time to check a blood sugar after a meal. Most experts recommend checking two hours after a meal. However, I am really confused by this. What if a person eats a high fat meal or eats foods that are high on the glycemic index? What if a person who is on a pump does a two hour extended bolus? Please help me understand what we do with that information after checking at two hours if all of the insulin has not been delivered. If the food is still elevating the blood sugar, why check after two hours? It seems like a wasted fingerpoke to me. Why not check after four hours when most of the insulin has been utilized? After all, isn’t the duration of most rapid acting insulins three and a half to four hours? Please help me understand this rationale.

You are asking a very specific time oriented question and so a lot of the answer would depend upon what you are trying to find out. The peak of most rapid acting analogs of insulin is about one to two hours and the tail lasts about four hours. So, for a faster acting food absorption question, about two hours gives sufficient information to help judge whether or not the bolus dose was a correct one. Once you change the food equation and add more (or less fat), then the question changes and the answer you would receive also changes, obviously. So, you are correct that a higher fat food would take longer to leave the stomach, therefore, slow down how the food is broken down/digested and absorbed and slow down the glycemic effect of that combination food. The real answer then depends upon getting sufficient blood glucose information to create a glycemic profile of prior to the meal, peak of insulin, peak of food absorbed, effect of activity, etc. So, one might get a one to two hour blood glucose check, and also a three to four hour check. If there were enough high fat or other evidence for slower absorbed (low glycemic index foods with a lot of fiber, for instance), then one would also add a five to six hour check. How much information is needed and what is practical goes into the exact answer and this depends upon all these circumstances and the goals of the monitoring. When the question is asked in a very general fashion, then the answer is usually somewhat more generalized and talks about prior to eating (preprandial) and postprandial (about one to two hours afterwards).

If you wanted information about peaks of NPH or Lantus, one would look at alternative times as well. If you wanted information about middle-of-the night problems, similarly you would get different answers and times to check.

SB