Special thanks to Bob Burnett
his assistance with this HOWTO.
A square wave bolus is an insulin bolus delivered with an insulin pump over an extended period of time. The time range is usually from 1/2 hour to 3 hours.
Some pumpers utilize this tool to match the rate of food digestion with the rate of insulin activity by spreading the bolus over the length of time it takes to digest a meal. One way to accomplish this is to deliver a portion (perhaps half) of the meal bolus at the beginning of a meal and then deliver the rest in a square wave over the next two hours or so. Other pumpers use the square wave to reduce the spike in insulin activity. For instance, when blood glucose is a little on the low side at the beginning of a meal, one might wish to deliver the insulin over the next half hour, thus giving the food a chance to start working before the insulin activity peaks.
The square wave bolus is useful for lengthy meals or prolonged snacking such as at a reception or banquet; for someone with gastroparesis; or whenever extending the effect of the insulin is desired. This is sometimes referred to as the pizza bolus because the fat in pizza tends to slow down glucose absorption, resulting in a delayed rise in blood glucose.
The human metabolism varies from person to person and some experimentation may be required to determine what time frame works best for you. The times given in this article are only examples and should be considered as a starting point, not set in stone.
You should consult with your physician and health care team when making changes to your insulin regimen.