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Bolus Insulin Types

Switch the insulin type and watch the same meal, at the same dose, play out completely differently — because each insulin peaks and lasts for a different length of time.

"Bolus" (mealtime) insulin isn't one thing. It ranges from the near-instant response of a pancreas without diabetes to Regular insulin, which takes half an hour just to start. Every one of them eventually brings blood sugar back down — but when they act and how long they stay in you is very different, and that changes how you have to dose.

Every insulin here uses the same correct dose for the meal — the same insulin-to-carb ratio — so they all bring blood sugar back to baseline in the end. What changes is how they get there: when they start, when they peak, and how long they last. Even with a perfect ratio, that shape is what decides how you have to use each one. Start with Endogenous to see how a non-diabetic's body reacts, then compare each injected insulin to it.

Pay attention to:

For educational purposes only. These curves are approximations of published insulin profiles — not dosing advice. Onset, peak, and duration vary by person, dose, and injection site.

What's happening here?

The chart shows a meal (the carb curve) and the insulin covering it, with the resulting blood sugar in blue. Every insulin gets the same dose — enough to fully cover the meal and return to baseline — so any difference you see comes purely from the insulin's shape.

Endogenous insulin — what the pancreas makes in a person without diabetes — behaves differently from every injected option, so it's modeled differently here. Beta cells sense blood glucose rising and release insulin to match it: a quick first-phase burst as glucose climbs, then a steady second-phase flow that tracks the meal and shuts off the moment blood sugar is back to normal, so it never overshoots. That's why it isn't dosed at a set time and nothing about it is adjustable — the body does it automatically, second by second. Switch the meal to Mixed / High Fat and watch it adapt: a slower meal draws a lower, longer, more spread-out release, like a series of small doses over hours. It's here as a reference, not a target: injected insulin — insulin delivered from outside the body — can't reproduce this continuous, automatic matching exactly. Seeing what a non-diabetic pancreas does makes the trade-offs of each injected insulin below clearer, and helps you get the most out of the ones you use.

Inhaled (Afrezza) is the closest injected match — it starts almost instantly and is mostly gone by ~3 hours. Rapid-Acting (aspart, lispro, glulisine) starts in ~10-15 minutes and peaks around 75 minutes, so a short pre-bolus lines it up nicely. Each has its own best timing.

Regular is the outlier. It's easy to assume any mealtime insulin acts fast — Regular ("short-acting") doesn't. It takes ~30 minutes to start and doesn't peak until ~2.5 hours, then keeps working for up to 8. Dose it at the first bite the way you would rapid-acting and blood sugar spikes while you wait (you can see the tall early rise), then its long tail can drop you hours later. Regular really needs a 30-45 minute pre-bolus — a very different habit, and the reason switching to or from Regular means re-learning your timing.

Applying this to your own life

Knowing which insulin you take isn't a detail — it tells you how long it's in you, when it peaks, and how far ahead to dose. To use yours well:

  • Know your insulin's peak and duration. Two people injecting the same units of different insulins for the same meal can end up with very different blood sugar.
  • Match your pre-bolus to the insulin. Rapid-acting likes 15-30 minutes ahead; Regular needs 30-45; inhaled goes at the first bite.
  • Watch the tail. Longer-acting bolus insulins like Regular keep working for hours after the meal is covered — a real late-low risk.
  • Don't assume they're interchangeable. Switching insulins usually means changing your timing, not just the vial — check with your care team.