Insulin on board, active insulin, or duration of insulin are terms you might hear in Facebook groups or see on your pump. The term is used with insulin pumps but the term or words you might hear for injections is “stacking insulin.”
Questions about insulin on board is one I hear a lot! I explain it during a pump training, but with all that is learned in a pump training and information overload, I usually get that question again later.
Insulin on Board or Active Insulin
These terms are referring to quick acting insulin, which is Novolog, Humalog or Apidra. The time the insulin is “active” in your system is about 3-4 hours. This is a setting in insulin pumps. This is determined by your physician and different doctors prefer different numbers. If you are finding that your blood sugar needs multiple corrections or the pump doesn’t allow you to correct til way after when you think it should, talk with your doctor about changing that number.
What Does It Mean?
Active insulin is a safety factor for pumps to prevent low blood sugars. It allows the pump to subtract out “insulin on board” from previous doses.
So, let’s say your blood sugar is 300 and you give a dose. If you check again in an hour and it is 200, and you enter 200 into your pump, it will not give you another correction. It knows that you still have “insulin on board” from the previous dose.
If you bolus for carbs only, then go back an hour or so later with a high blood sugar, it will subtract out some of the correction dose for the “active insulin” from the carbs.
The pumps are very smart, so trust the doses recommended. If you are having to override the suggested doses, it means your pump settings are not correct. Talk with your doctor about setting changes. Kids may need frequent changes due to growth and increased insulin needs as they age.
How does it pertain to injections?
You may hear the term “stacking insulin.” With injections, the same concept exists. Frequently patients are told to not inject a correction dose within 3-4 hours of the last injection. This is the manual way of subtracting out “active insulin.” That last shot is still working to lower the blood sugar.
Hope that helps! Add any questions in the comments!
A funny story about active insulin is I have an older patient who calls it “pending insulin.” It was hard to get him to understand the concept. He would add extra carbs to his bolus that he didn’t eat in order to get a larger dose and then go low. We had to finally tell him to stop and trust that his “pending insulin” would kick in and lower him.