Insulin Types Explained: Onset, Peak & Duration
By Ryan Mitchell · Reviewed against ADA Standards of Care · Updated July 2026
Every insulin does the same job — moving glucose out of the blood — but the five classes differ in when they start (onset), when they work hardest (peak), and how long they last (duration). Those three numbers decide what role each insulin plays in a regimen, which dosing rule applies to it, and how it interacts with meals and corrections.
The complete onset–peak–duration chart
| Class | Generic (brand) | Onset | Peak | Duration | Role |
|---|---|---|---|---|---|
| Ultra-rapid | faster aspart (Fiasp), lispro-aabc (Lyumjev) | 2–15 min | ~1 h | 3–5 h | Mealtime bolus, minimal pre-bolus |
| Rapid-acting | lispro (Humalog), aspart (NovoLog), glulisine (Apidra) | 10–20 min | 1–2 h | 3–5 h | Mealtime bolus & corrections (500/1800 Rules) |
| Short-acting (Regular) | Humulin R, Novolin R | 30–60 min | 2–4 h | 6–8 h | Meals with 30-min lead (450/1500 Rules); IV drips |
| Intermediate | NPH (Humulin N, Novolin N) | 1–2 h | 4–8 h | 12–18 h | Twice-daily basal in some regimens |
| Long-acting | glargine (Lantus, Basaglar), detemir (Levemir) | 1–2 h | Minimal / flat | ~20–24 h | Once/twice-daily basal |
| Ultra-long | degludec (Tresiba), glargine U-300 (Toujeo) | 1–6 h | None (flat) | 36–42 h | Once-daily basal, flexible timing |
Why the times matter for dosing math
- Which carb-ratio rule applies. Rapid analogs use the 500 Rule; Regular insulin's longer overlap uses the 450 Rule.
- Pre-bolus timing. Rapid insulin is typically taken 10–20 minutes before eating; Regular needs ~30 minutes. Our timing calculator adjusts for your current glucose.
- Insulin on board. Duration defines how long a bolus keeps working — the basis of IOB calculations and stacking prevention. Rapid analogs are usually modeled at 3–5 hours.
- Hypo-risk windows. Peaking insulins (NPH, Regular) create predictable low-risk windows; flat basals don't. This is why NPH regimens require more structured meal timing.
Premixed insulins
Premixed products (70/30, 75/25, 50/50) combine intermediate insulin with rapid or Regular insulin in one injection — e.g., Humulin 70/30 is 70% NPH + 30% Regular. They trade flexibility for simplicity: fewer injections, but meals must be consistent because the mix can't be adjusted per-meal. Dosing conversions between regimens are care-team territory.
Concentrations: U-100, U-40, U-500
Most human insulin is U-100 (100 units/mL). U-500 Regular exists for severe insulin resistance, and U-40 is common in veterinary insulin (see the cat and dog calculators). Matching syringe to concentration is a safety-critical step — our units-to-mL converter and syringe-reading guide cover it in detail.
Sources & References
- American Diabetes Association. Standards of Medical Care in Diabetes — 2024. Section 9. Link
- NIDDK. Insulin Medicines & Treatments. Link
- Donner T, Sarkar S. Insulin – Pharmacology, Therapeutic Regimens. In: Endotext. Link
Last reviewed: July 2026 · See our methodology