The Importance of Timing of Food and Diabetic Medication

By Alan L. Rubin, Cait James

If you take insulin, the peak of your insulin activity should correspond with the greatest availability of glucose in your blood. To accomplish this, you need to know the time when your insulin is most active, how long it lasts, and when it is no longer active.

  • Regular insulin, which has been around for decades, takes 30 minutes to start to lower the glucose level, peaks at three hours, and is gone by six to eight hours. This insulin is used before meals to keep glucose low until the next meal.

    The problem with regular insulin has always been that you have to take it 30 minutes before you eat or run the risk of becoming hypoglycemic at first, and hyperglycemic later when the insulin is no longer around but your food is providing glucose.

  • Rapid-acting lispro insulin and insulin glulisine are the newest preparations and the shortest acting. They begin to lower the glucose level within five minutes after administration, peak at about one hour, and are no longer active by about three hours.

    These insulins are a great advance because they free the person with diabetes to take a shot only when he or she eats. Because their activity begins and ends so quickly, they don’t cause hypoglycemia as often as the older preparation.

Given a choice, because of its rapid onset and fall-off in activity, choose either lispro or glulisine as the short-acting insulins for people with type 1 diabetes and those with type 2 diabetes who take insulin.

If you’re going out to eat, you rarely know when the food will be served. Using rapid-acting insulins, you can measure your blood glucose when the food arrives and take an immediate shot. These preparations really free you to take insulin when you need it. They add a level of flexibility to your schedule that didn’t exist before.

If you take regular insulin, keep to a more regular schedule of eating. In addition to short-acting insulin, if you have type 1 diabetes, or in some instances type 2 diabetes, you need to take a longer-acting preparation.

The reason is to ensure that some insulin is always circulating to keep your body’s metabolism running smoothly. Insulin glargine and insulin detemir are preparations that have no peak of activity but are available for 24 hours. You take one shot daily at bedtime, and they cover your needs for insulin except when large amounts of glucose enter your blood after meals. That is what rapid-acting insulins are for.

Each person responds in his or her own way to different preparations of insulin. You need to test your blood glucose to determine your individual response.

An additional factor affecting the onset of insulin is the location of the injection. Because your abdominal muscles are usually at rest, injection of insulin into the abdomen results in more consistent blood glucose levels. If you use the arms or legs, the insulin will be taken up faster or slower, depending on whether you exercise or not. Be sure to rotate sites.

The depth of the injection also affects the onset of activity of the insulin. A deeper injection results in a faster onset of action. If you use the same length needle and insert it to its maximum length each time, you’ll ensure more uniform activity.

A great deal of variation is possible in the taking of an insulin shot. It’s no wonder that people who must inject insulin tend to have many more ups and downs in their blood glucose. But with proper education, these variations can be reduced.

If you take oral medication, in particular the sulfonylurea drugs like micronase and glucotrol, the timing of food in relation to the taking of your medication must also be considered.