Insulin Basics: The Types of Insulin At-A-Glance

Comparison of Human Insulin Preparations and Analogs

Revised May 2026. Onset/peak/duration values reconciled with the At-A-Glance chart and reflect FDA prescribing information and common clinical teaching ranges. Always defer to the current product label.

Rapid-acting Insulin: This type of insulin starts to work within 15 minutes of injection and peaks between 1 to 3 hours after injection. Duration is generally 3 to 5 hours. Some resources further divide them into very rapid acting with an onset of roughly 15 to 20 minutes from injection and rapid acting with an onset of action between 15 to 30 minutes.

Examples include insulin lispro (brand names: Admelog, Humalog), lispro-aabc (brand name: Lyumjev), insulin aspart (brand names: Fiasp, NovoLog), and insulin glulisine (brand name: Apidra).

In this list, Fiasp and Lyumjev are considered very rapid-acting insulins.

A very rapid-acting inhaled insulin is also available. It starts to work within about 12 to 15 minutes, peaks within 35 to 55 minutes, and has a duration of roughly 1.5 to 3 hours. This rapid-acting inhaled insulin, known by the brand name Afrezza, is an inhaled powder form of regular human insulin.

Short-acting Insulin: This type of insulin takes about 30 minutes to start working and peaks at about 2 to 3 hours after injection. The effective duration is approximately 5 to 8 hours.

Examples include regular insulin (brand names: Humulin R, Novolin R).

Intermediate-acting Insulin: This type of insulin takes about 2 to 4 hours to start working and peaks at about 4 to 10 hours after injection. The effective duration is approximately 10 to 16 hours.

Examples include NPH insulin (brand names: Humulin N, Novolin N).

Long-acting Insulin: This type of insulin starts working several hours after injection and can last up to 24 hours or more, depending on the agent. Examples include insulin glargine (brand names: Lantus, Basaglar, Toujeo), insulin detemir (brand name: Levemir — discontinued in the U.S. as of December 2024; see Availability Watch), and insulin degludec (brand name: Tresiba), which is ultra-long-acting with a duration of up to ~42 hours.

A once-weekly basal insulin is now available (see below).

Combination Insulin / Pre-Mixed / Fixed Combination: This type of insulin combines different types of insulin into one injection. It starts working within 5 to 60 minutes, produces dual peaks, and has an effective duration of approximately 10 to 16 hours.

Examples include the brand names: Humalog Mix 75/25, Humalog Mix 50/50, NovoLog Mix 70/30, and Novolin 70/30.

Insulin Concentration Details

Insulin also comes in different concentrations. The concentration of insulin identifies the number of units of insulin in 1 milliliter (mL). The most commonly used concentration in the United States is U-100. Higher concentrations are used to decrease the volume of injection needed to administer a dose and are used when larger amounts of insulin are required for glucose management.

Insulin delivery devices including smart pens, insulin pumps, and insulin patch devices are approved for use with certain insulins. Consult the manufacturer's website for the most up-to-date list of approved insulins for a particular device.

Insulin Concentration Quick Guide

Several insulins are available in concentrated formulations. Key clinical pearls:

Lispro U-200 (Humalog® U-200)

• Pen dials in 1-unit increments; max 60 units/injection
• No dose conversion needed when switching from U-100 pens

Degludec U-200 (Tresiba® U-200)

• Duration: up to ~42 hours
• Available only in FlexTouch® pen; max 160 units/injection
• No dose conversion between U-100 and U-200 pens

Glargine U-300 (Toujeo®)

• Flatter, longer profile than U-100 glargine (up to ~36 hours)
• Comes only in SoloStar®/Max SoloStar® pens; max 80 units/injection
• Do not extract with syringes; use only pen device

Regular insulin U-500 (Humulin® R U-500)

• Acts more like NPH at higher volumes; provides both basal and bolus coverage
• Requires dedicated U-500 pen or syringe; high risk for dosing errors if miscalculated; max 250–300 units/injection depending on the delivery device

Insulin icodec U-700 (Awiqli®) — NEW

• Once-weekly basal insulin; ~7-day duration
• High-concentration U-700; do not withdraw from the pen with a syringe and do not mix or dilute
• See Availability Watch for approval/launch status

Availability Watch

Levemir® (insulin detemir) was discontinued in the U.S. — the FlexPen as of April 1, 2024, and vials after December 31, 2024. Transition planning is recommended for anyone previously using this basal insulin. Reach out to the Novo Nordisk Customer Care Center at 800-727-6500 with questions.

Fiasp® (faster aspart) remains FDA-approved, but certain presentations have been on allocation/shortage in the U.S. — check current pharmacy supply when prescribing.

Once-weekly insulin icodec (Awiqli®) was approved by the FDA on March 26, 2026, as the first once-weekly basal insulin (U-700) for adults with type 2 diabetes. It is not approved for type 1 diabetes (the FDA declined the T1D indication in 2024 over hypoglycemia risk) and not approved for children. U.S. launch is expected in the second half of 2026, so it may not yet be available at all pharmacies. Awiqli is also approved in the EU, Canada, Japan, Australia, and other countries.

Biosimilar & Interchangeable Insulins

Insulin glargine-yfgn (Semglee®) and glargine-aglr (Rezvoglar®) are FDA-designated interchangeable with Lantus®.

Pharmacies may substitute these products depending on state laws and payer requirements. Clinicians should inform patients about potential substitutions and check formulary preferences.

Afrezza® Safety Box

• Contraindicated in patients with chronic lung disease (asthma, COPD).
• Baseline spirometry (FEV1) required before initiation; repeat at six (6) months and annually thereafter.
• Not studied in smokers or recent ex-smokers; use caution.
• Remind patients: cough and throat irritation are common side effects.

Reminder: Ongoing Evaluation and Adjustments Are Needed

It is important to remember that a "set it and forget it" approach to insulin does not work for an individual on insulin therapy. It is necessary to continually evaluate a person's insulin plan over time based on data on its effectiveness. Using the published information on onset, peak, and duration of action (see chart) is a useful starting point that will need to be adjusted based on the numerous factors that continually impact the lives of people with diabetes.

Related Links

View and compare all insulins and devices

Insulin – biosimilars and interchangeables