Split Bolus Simulator
See how splitting your bolus into two doses at different times can improve coverage for mixed meals.
A split bolus divides your total insulin dose into two injections given at different times. Instead of giving all your insulin upfront, part is given earlier and the rest is given later.
This chart is designed to help you visualize how splitting a bolus changes the shape of the insulin action curve and how it matches differently to meal absorption — especially for high-fat meals that digest slowly.
Pay attention to:
- What happens when most insulin is given upfront for a high-fat meal?
- What happens when too much insulin is delayed?
- When does splitting the bolus smooth the blood sugar curve?
What's happening here?
Fast-acting insulin peaks around one hour after dosing and can last up to six hours. When you give the entire bolus upfront, most of the insulin's strongest action happens early.
For carbohydrate-only meals:
- A single upfront bolus often matches digestion better than splitting.
- Pre-bolusing (giving insulin 10–30 minutes before eating) may better match insulin action to carb absorption.
For high-fat meals:
- Fat slows digestion, so a pre-bolus might increase the risk of an early low before food absorbs.
- If all insulin is given upfront, it may start working before food digests, causing an early blood sugar drop.
- If too much insulin is delayed, you may see an early high followed by a late drop.
Applying this to your own life
When eating high fat and protein meals, look at how the timing of insulin boluses result in blood sugar changes similar or different to what you notice in this chart. As you make observations, keep notes on what different bolus times and split amounts result in with different meals.
Pay attention to:
- What happens if most of the insulin is given upfront?
- What happens if too much insulin is delayed?
- How does adding fat change the timing of the glucose rise?
- When does spreading insulin action smooth the curve?