A built-in bolus calculator uses personalized settings to make bolus doses more accurate and less likely to cause insulin stacking from prior boluses. The pump bolus calculator allows bolus recommendations to match the carbs you eat, bring down high readings, and minimize insulin stacking. For optimal glucose results, these bolus calculator settings are adjusted:
- Basal rates
- Carb factor
- Correction factor
- Correction target or target range
- Duration of insulin action (DIA)
The pump bolus calculator uses these settings and its internal logic, plus a carb count and glucose reading from the wearer, to recommend accurate bolus doses. There are, however, some differences in how pumps calculate bolus doses. All BCs count carb boluses and correction boluses as bolus on board (discussed below), except the 2012 and earlier Omnipods that do not include carb boluses in bolus on board.
However, most current bolus calculators do not subtract excess bolus on board from carb boluses. This can cause excessive bolus recommendations in some situations, such as when someone wants to eat carbs at bedtime but they have BOB with a relatively normal glucose reading. It is important to know how your pump handles active insulin or bolus on board when boluses are given. This is detailed in the 5th edition of Pumping Insulin.
Dr. Irl Hirsch at the Univ. of Washington suggests that the bolus calculator recommendation may need to be overridden as often as 25% of the time to give a more appropriate bolus in light of circumstances the wearer knows but the pump does not. Recommended bolus doses can usually be more accruately adjusted by a pumper when they wear a CGM that shows their glucose trend.
8.12 Times to Override Your Bolus Calculator Recommendation:
You know a lot more about your circumstances than your pump BC when you give a bolus, especially if you wear a CGM. Some situations require that you override your BC bolus recommendation entirely or modify it with more carbs or more or less insulin:
- Before, during, and after exercise or increased activity, carb and correction bolus recommendations may need to be cut by as much as a half. A temp basal reduction and free carbs may also be needed.
- With an infection, stress, or menses, increased basal rates and carb and correction boluses are often needed. • When your CGM shows a glucose trend line going high or low.
- At bedtime is an especially important time to double-check bolus recommendations to avoid excess insulin stacking.
Tips on Bolus Calculators
- Know how your pump handles BOB in its carb or correction bolus recommendations.
- Know where to find your current BOB (residual bolus insulin, insulin on board,
active insulin) on a pump screen. - Adjust bolus recommendations before and after exercise, during illnesses or infections,
during stress, with menses, etc. - Your CGM shows your approximate glucose value, trend line, and arrows and
alarms that indicate impending highs and lows. Your CGM information helps you
know when to override a BC bolus recommendation. - With normal glucose, check your BOB before you assume that everything is fine.
- When your reading is low, check your pump to see how much BOB is left.
- Never give a bolus that doesn’t seem right to you.
- Double-check your pump settings if bolus recommendations often don’t seem right.
For good glucose outcomes, it is important that your insulin pump bolus calculator has settings that work for you. Ensure that you know how your BC works, and gradually learn when to override its bolus recommendation.