Insulin Types Explained
A complete reference for all insulin types: rapid-acting, short-acting (Regular), intermediate-acting (NPH), long-acting, and ultra-long-acting. Covers onset, peak, duration, brand names, and the clinical role of each type.
Rapid-Acting Insulin (Bolus)
Rapid-acting analogues are used for meals and corrections. They act quickly and peak within 1–2 hours, matching the rise in blood glucose from eating.
| Generic Name | Brand(s) | Onset | Peak | Duration |
|---|---|---|---|---|
| Insulin lispro | Humalog, Admelog | 10–15 min | 1–2 hr | 3–5 hr |
| Insulin aspart | NovoLog, Fiasp | 10–20 min | 1–3 hr | 3–5 hr |
| Insulin glulisine | Apidra | 10–15 min | 1 hr | 3–4 hr |
| Faster insulin aspart | Fiasp | 2–5 min | 1–2 hr | 3–5 hr |
| Insulin lispro-aabc | Lyumjev | ~5 min | ~1 hr | ~5 hr |
Rapid-acting insulins are typically injected 0–15 minutes before eating. The ultra-fast formulations (Fiasp, Lyumjev) can be given at the start of the meal or even immediately after — useful for unpredictable eaters.
Short-Acting Insulin (Regular)
Regular insulin (also called R insulin) is the original "mealtime" insulin. It has a slower onset and longer tail than rapid-acting analogues, requiring injection 30 minutes before meals.
| Generic Name | Brand(s) | Onset | Peak | Duration |
|---|---|---|---|---|
| Regular insulin | Humulin R, Novolin R | 30–60 min | 2–4 hr | 5–8 hr |
| Regular U-500 | Humulin R U-500 | 30 min | 4–8 hr | Up to 24 hr |
Regular insulin uses the 1500 Rule for ISF estimation (vs 1800 Rule for rapid-acting). It is also used for IV infusions. U-500 is reserved for highly insulin-resistant patients using very large doses.
Intermediate-Acting Insulin (NPH)
| Generic Name | Brand(s) | Onset | Peak | Duration |
|---|---|---|---|---|
| NPH (isophane) | Humulin N, Novolin N | 1–2 hr | 4–12 hr | 14–24 hr |
NPH has a distinct peak, giving it more hypoglycemia risk than modern long-acting analogues. It requires twice-daily dosing and is now used primarily in cost-constrained settings. NPH is the only insulin approved for mixing with Regular insulin in the same syringe (pre-mixed formulations).
Long-Acting Insulin (Basal)
Long-acting analogues provide peakless background ("basal") insulin coverage for 20–24 hours, closely mimicking the body's continuous low-level insulin secretion.
| Generic Name | Brand(s) | Onset | Peak | Duration |
|---|---|---|---|---|
| Glargine U-100 | Lantus, Basaglar, Semglee | 2–4 hr | Peakless | ~24 hr |
| Glargine U-300 | Toujeo | 6 hr | Peakless | ~36 hr |
| Detemir | Levemir | 1–2 hr | Mild peak | 18–22 hr |
Glargine U-100 is the most widely prescribed long-acting insulin. Toujeo (U-300) delivers the same daily units in one-third the volume, with a flatter, longer profile and less nocturnal hypoglycemia. Detemir often requires twice-daily dosing at higher doses.
Ultra-Long-Acting Insulin
| Generic Name | Brand | Onset | Peak | Duration |
|---|---|---|---|---|
| Degludec U-100/U-200 | Tresiba | ~1 hr | Peakless | > 42 hr |
Degludec reaches steady state after 2–3 days and provides extremely stable coverage. Its ultra-long duration allows flexible dosing timing — doses can be shifted by up to 8 hours without clinically significant impact. Less dawn phenomenon effect than glargine.
Pre-Mixed Insulins
Pre-mixed formulations combine a basal and bolus insulin in a fixed ratio. Convenient but less flexible — dose adjustments affect both components simultaneously.
| Product | Ratio | Components |
|---|---|---|
| Humulin 70/30 | 70% / 30% | NPH + Regular |
| NovoLog Mix 70/30 | 70% / 30% | Protamine aspart + aspart |
| Humalog Mix 75/25 | 75% / 25% | Protamine lispro + lispro |
Sources
- American Diabetes Association. Standards of Medical Care — 2024.
- Hirsch IB. "Insulin analogues." N Engl J Med. 2005;352:174–183.
Last reviewed: June 2025