Another class of oral diabetes medicines called alpha-glucosidase inhibitors (which includes the drugs Precose and Glyset) lowers after-meal blood glucose levels by partially blocking the transport of sugars across the intestines and into the bloodstream. However, these medicines can sometimes cause gas, bloating, and gastrointestinal upset, so the pros of taking them don’t always outweigh the cons.
Time your bolus insulin properly. For people who take rapid-acting insulin at mealtimes, the timing of the bolus can have a huge impact on after-meal blood glucose levels. Boluses given too late to match the entry of glucose from dietary carbohydrates into the bloodstream can produce significant blood glucose spikes soon after eating. A properly timed bolus, on the other hand, can result in excellent after-meal control.
Unless you have gastroparesis (slowed stomach emptying, usually caused by nerve damage), it is best to give bolus insulin doses before eating. How long before? It depends mainly on what you are eating and on your pre-meal blood glucose level.
Figuring out the pre-meal blood glucose part is fairly straightforward: the higher your blood glucose, the earlier the bolus should be given. If your pre-meal blood glucose is well above your target, it is best to give the bolus and then wait at least 30 minutes before eating. Near your target blood glucose? Wait 15 minutes. Below target? Either take the bolus and eat right away, or take the bolus after eating.
The “what you are eating” part is a bit more complex. Essentially, the higher the glycemic index of the food, the earlier the bolus should be given. The glycemic index is a ranking of how quickly a food is broken down during digestion and raises blood glucose. Foods with a high glycemic index (greater than 70) include most cold breakfast cereals, breads, potatoes, rice, and snack chips. They tend to cause a significant rise in blood glucose about 30–45 minutes after they are eaten. For meals consisting of mainly high-glycemic-index foods, it is best to bolus 15–20 minutes before eating. This will allow the insulin peak to coincide as closely as possible with the blood glucose peak.
Foods with a moderate glycemic index (approximately 45–70) digest a bit slower, resulting in a slightly less pronounced blood glucose peak approximately 45–60 minutes after eating. Examples include ice cream, orange juice, cake, carrots, pizza, and meals that include a variety of foods. It is best to bolus 5–10 minutes before eating foods with a moderate glycemic index.
Foods with a low glycemic index (below 45) tend to cause a slow, gradual blood glucose rise. The blood glucose “peak” is usually modest and may occur an hour or two after eating. Examples of foods with a low glycemic index include pasta, milk, yogurt, and cooked, dried beans. For these types of foods, bolusing right at the start of the meal, during the meal, or right after the meal usually works best.
Does earlier bolusing make a difference? Absolutely. Research has shown that simply giving mealtime boluses before eating rather than after eating can reduce the post-meal spike by about 50 mg/dl.
Use a “super bolus.” For people who use insulin pumps, one way to have more insulin working right after eating and less working several hours later is to give what John Walsh, coauthor of the Pumping Insulin books, calls a “super bolus.” This is done by substantially reducing the basal rate for 3 hours before eating, then adding the amount of insulin that wasn’t given as basal insulin to the normal pre-meal bolus. For example, if your normal basal rate in the morning is 0.6 units per hour, you could set a temporary basal rate of 10% (90% reduction), for the 3 hours before breakfast, then bolus an extra 1.8 units at breakfast.