Insulin Types Explained: Onset, Peak & Duration
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — October 2026
By Ryan Mitchell
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.
Quick answer: there are five insulin types, defined by how fast they start and how long they last: rapid-acting (onset ~15 min, lasts 3–5 h), short-acting regular (30 min, 6–8 h), intermediate NPH (1–2 h, 12–18 h), long-acting analogues (1–2 h, 20–24 h or beyond) and ultra-long degludec (~1 h, 42 h). The full chart with every value is below, followed by brand names for each type.
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 — discontinued in the US end-2024) | 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) | Over 24 h (Toujeo); over 42 h (Tresiba) | Once-daily basal, flexible timing |
Brand names by insulin type
Chart values are generic; this is what those names look like at the pharmacy. Brand insulin used to be far cheaper, and the authorised-generic switch has been closing that gap — but many prescriptions still use the brand name, so it pays to know which category your pen or vial belongs to.
| Type | Generic name | Common brands | Typical use |
|---|---|---|---|
| Rapid-acting | insulin lispro, aspart, glulisine | Humalog, NovoLog, Fiasp, Apidra | Bolus at meals; also pump use |
| Short-acting | regular human insulin | Humulin R, Novolin R | Meal coverage taken 30 min early; IV infusions |
| Intermediate | NPH (isophane) | Humulin N, Novolin N | Twice-daily basal; steroid-hyperglycemia protocols |
| Long-acting | glargine, detemir | Lantus, Basaglar, Toujeo (U-300), Levemir (discontinued) | Once-daily basal (detemir often twice-daily) |
| Ultra-long | insulin degludec | Tresiba | Once-daily basal with 42 h duration |
| Premixed | fixed NPH/regular or analogue mixes | Humulin 70/30, NovoLog Mix 70/30, Humalog Mix 75/25 | Twice-daily combined coverage |
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.
How many types of insulin are there?
Five classes are counted in almost every clinical list: rapid-acting, short-acting (also called regular), intermediate-acting (NPH), long-acting, and ultra-long-acting. Inhaled insulin is usually treated as a sixth category because it is a different route rather than a different duration, and premixed products are combinations of two of the five rather than a class of their own.
Counts differ between sources mainly over those two edge cases. A list that says four has usually merged long-acting and ultra-long-acting; a list that says six has counted inhaled insulin separately. The table above sets out each class with its onset, peak and duration, which matters more for dosing than the label.
Insulin peak times at a glance
The peak is when an insulin is working hardest, and it is the number that decides timing. Rapid-acting insulins peak about one to two hours after injection, and the ultra-rapid formulations closer to one hour, which is why they are taken near a meal. Long-acting insulins are designed to have no pronounced peak at all, so they hold a steady background level instead.
Two practical consequences follow. A hypo that arrives two hours after a meal often points at mealtime insulin rather than basal, because that is when rapid-acting insulin peaks. And a basal insulin that produces a clear peak is behaving unlike its label, which is worth raising with a prescriber.
The complete chart above gives onset, peak and duration side by side for every class, which is the comparison most people are actually looking for when they search for an insulin chart. Comparing two insulins means comparing those three numbers, not just the brand names.
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. Dose maths for each insulin type is covered by our free insulin calculators.
Inhaled insulin, the sixth category
One mealtime insulin is not injected at all. Afrezza is an insulin human inhalation powder taken through a small inhaler at the start of a meal, and its action profile is faster than any injected analogue.
| Property | Afrezza (inhaled) | Rapid analogue, for comparison |
|---|---|---|
| Onset | About 12 minutes | About 15 minutes |
| Peak | 35–45 minutes, by cartridge size | 1–3 hours |
| Duration | 1.5–3 hours | 3–5 hours |
| Dosing unit | Cartridges of 4, 8 and 12 units | Any whole or half unit |
The short tail is the practical appeal: insulin clears well before an injected analogue would, which narrows the window for a late post-meal low. The cartridge sizes are the trade-off, because doses step in fours rather than ones and cannot be fine-tuned the way a pen can.
Lung safety restrictions. Afrezza carries a boxed warning for acute bronchospasm and is contraindicated in people with chronic lung disease such as asthma or COPD. Prescribers perform spirometry to measure FEV1 before starting it, and repeat lung-function testing during treatment. It is not an option that can be switched to casually.
Frequently Asked Questions: Insulin Types Explained
How long does rapid-acting insulin take to work?
Rapid-acting analogues such as lispro, aspart and glulisine generally begin working within about 15 minutes, peak around 1–2 hours, and are largely finished by 4–5 hours. Ultra-rapid formulations act sooner still. Regular human insulin is slower on every count, typically starting around 30 minutes and peaking at 2–4 hours.
What is the difference between basal and bolus insulin?
Basal insulin is the background supply that holds glucose steady between meals and overnight, delivered by a long-acting insulin or a pump’s continuous rate. Bolus insulin is the fast-acting dose taken to cover a meal or correct a high reading. A common starting split is roughly half the total daily dose as basal and half as bolus.
What does U-100 mean?
It is the concentration: 100 units of insulin per millilitre, which is the standard for human insulin products. U-40 holds 40 units per mL and is mostly veterinary, while U-500 is five times as concentrated as U-100 and reserved for severe insulin resistance. Mismatching concentration and syringe is a well-documented cause of serious dosing errors.
What are premixed insulins?
They combine a fixed proportion of intermediate and rapid or short-acting insulin in one pen or vial — 70/30 and 75/25 are common. They reduce the number of daily injections, which suits some people, but the fixed ratio cannot be adjusted independently, so mealtime flexibility is lower than with a separate basal-bolus regimen.
Why does duration of action matter for dosing?
Because doses overlap. If a previous rapid-acting dose is still active and you take another correction, the two stack and can drive glucose too low. Knowing how long your insulin actually works is what makes insulin-on-board calculations meaningful.
Sources & References
- American Diabetes Association. Standards of Care in Diabetes — 2026. Section 9. Link
- NIDDK. Insulin Medicines & Treatments. Link
- Donner T, Sarkar S. Insulin – Pharmacology, Therapeutic Regimens. In: Endotext. Link
Written by Ryan Mitchell · Last updated: October 2026