For those who take daytime intermediate-acting insulin, it can be difficult and dangerous to correct for high blood glucose until the intermediate-acting insulin has worn off. NPH insulin does not always get absorbed or act in a predictable manner. In general, to avoid hypoglycemia, it is best to wait at least 10 hours after taking NPH before correcting for high readings.
5. Adjust doses based on carbohydrate intake.
Of everything you eat, carbohydrate has the most profound influence on blood glucose levels. Virtually all forms of carbohydrate convert into blood glucose fairly rapidly. If your carbohydrate intake varies, your insulin and medicine doses should vary as well.
Carbohydrate also acts differently throughout the day. Most people need different doses of insulin or oral medicine to cover their carbohydrate at different meals. This is caused by varying levels of stress, insulin sensitivity, and physical activity throughout the day.
And if you’re going to go to the trouble of matching your doses to your carbohydrate intake, be sure that your carbohydrate counts are reasonably accurate. Look up the exact carbohydrate count for foods you are unfamiliar with. (An excellent resource for looking up carbohydrate counts is The Doctor’s Pocket Calorie, Fat and Carb Counter, which is available through your local bookstore or online.) Measure your portions. And don’t forget to deduct all of the fiber grams and half of the sugar alcohols from the total carbohydrate count; fiber is a carbohydrate that is not digested, and sugar alcohols only raise the blood glucose about half as much as an equivalent amount of ordinary carbohydrate.
6. Extend or delay your mealtime insulin when necessary.
Not all foods are digested at the same rate, so in some instances you will need to prolong your insulin’s action to prevent hypoglycemia after eating. For example, foods with a low glycemic index value (such as pasta, beans, and dairy products) usually take several hours to digest. With these kinds of foods, it might take 2–4 hours to see a significant blood glucose rise. (The glycemic index is a system of rating carbohydrate-containing foods based on how quickly they are absorbed; a food with a high glycemic index raises blood glucose levels faster than foods with a lower glycemic index.) If you were to take your full dose of rapid-acting insulin with your meal, the insulin would peak long before the blood glucose rises, resulting in hypoglycemia. To add insult to injury, your blood glucose may rise significantly several hours later once the mealtime insulin stops working and the food finally kicks in.
It is advisable to extend or delay your insulin when consuming food for a prolonged time, such as at a holiday meal or when eating a bucket of popcorn at the movies. Very large food portions also take a long time to digest. Think of your stomach as an hourglass and the food as sand trickling through. A very large portion of food, especially with a high fat content, might take several hours to pour through the stomach and into the intestines where it can be absorbed into the bloodstream, while a small portion will pour through relatively quickly.
In addition, a person who has gastroparesis (a nerve condition that causes the stomach to empty more slowly than usual) would also benefit from extending or delaying his mealtime insulin.
Extending or delaying insulin delivery can be accomplished in a number of ways. People who use mealtime rapid-acting insulin can take it 15–30 minutes after eating instead of before or during the meal. The dose could also be split into two injections — taking 50% with the meal and taking the other 50% an hour or two later. Alternatively, Regular insulin can be used instead of rapid-acting insulin when a slow-digesting meal is consumed.