Updated: Mar 18, 2020
Why are we constantly told to bolus 15-20 minutes before meals? It’s incredibly inconvenient, but necessary!
When it comes to insulin, timing is everything. In fact, incorrect timing is the MOST COMMON cause of post-meal BG spikes. Why? Because current “rapid-acting” insulin is just not rapid and when a bolus is given immediately before a meal (or worse, after a meal), the carbs are digested long before the insulin can effectively do its job. This causes a significant BG spike followed by normalization of BGs (if the correct dose was given).
So, if our BGs eventually normalize, why should we worry?
Current research regarding the development of DM complications has indicated that it is not only hyperglycemia and high HbA1c levels that lead to complications, but BG fluctuations as well. Plus, it feels terrible! Instead, if the bolus is given 15-20 minutes early, the insulin will kick in at the same time as carb digestion, eliminating the significant spike.
Though insulin timing is a common problem, It is not often thought about in the DM community as a cause of high BGs. Often, a significant post-prandial spike is thought to be due to an inaccurate dosage of insulin. Instead of strengthening your carb factor and giving more insulin for the meal, try giving the bolus earlier. If your timing is the problem, you may have been giving the correct dose all along and increasing the amount of insulin given could worsen the problem by causing lows.
So how do we know if our post-prandial spikes are caused by timing or by inadequate amounts of insulin? If the BG normalizes 4-5hrs after a meal (without additional insulin), then the problem is most likely time related. If the BG is elevated 4-5hrs post-meal, then insulin amount is more than likely the problem. If the BG spikes and is then followed by a low, then the problem is both; less insulin is needed and the bolus needs to be taken earlier.
Sometimes, planning can be difficult. It is not always easy to predict what you will eat or how much. I totally get it, and I have that problem. Here is what I do…
On average, I eat about 20 grams of carbs or more with my meals. If I am not sure what I am going to eat or if I will finish my meal I input 20 grams of carbs into my bolus wizard 15-20 minutes before my meal. I call this my “pre-bolus bolus”. Then, once my meal arrives, I bolus for the remaining amount of carbohydrates. This allows my insulin to begin working early, while still reducing my risk of hypoglycemia if my meal is later than expected. This method is easily done with a pump, but can also be done with injections (you will just need to take two injections instead of one). Try it!