Overview
Insulin is used to treat people who have diabetes. How quickly insulin starts to work and how long it lasts will be different depending on the type of insulin you use. Other factors that can affect insulin and your blood sugar are exercise, diet, illness, some medicines, stress, the dose, how you take it, or where you inject it. The table below is a general guide. Your results may be different.
Insulin is available in several strengths. U-100 is the most common. U-100 means there are 100 units of insulin in one milliliter of fluid. Other strengths include U-200, U-300, and U-500. For example, U-500 is five times more concentrated than U-100 regular insulin. Be sure to check the concentration of your insulin so you take the right amount.
Insulin is made by different companies. Ask your doctor or diabetes educator about the type of insulin you have and how to use it. See the table below for types of insulin and some examples.
Types of insulin
| Type |
Examples |
Appearance |
When it starts to work (onset) |
How long it lasts (duration) |
| Rapid-acting insulins (bolus insulin) are usually taken at the start of a meal. |
Insulin aspart (Fiasp)Insulin glulisine (Apidra)Insulin lispro (Humalog) |
Clear |
10–20 minutes |
2–4 hours |
| Rapid-acting insulin also comes in a form that can be inhaled through the mouth. |
Insulin human inhalation powder (Afrezza) |
Contained in a cartridge |
12 minutes |
1½–3 hours |
| Short-acting insulins (bolus insulin) are usually taken a short time before a meal. |
Insulin regular (Humulin-R U-100, Novolin R, and Novolin R ReliOn) |
Clear |
30–60 minutes |
5–8 hours |
| Intermediate-acting insulins (basal insulin) are usually taken between meals and at bedtime. |
Insulin NPH (Humulin-N, Novolin-N, and Novolin ReliOn) |
Cloudy |
1–3 hours |
Up to 24 hours |
| Long-acting insulins (basal insulin) are usually taken between meals and at bedtime. |
Insulin detemir (Levemir)Insulin glargine (Lantus and Basaglar)Insulin regular (Humulin R U-500) |
Clear |
60–90 minutes (30 minutes for U-500) |
Up to 24 hours |
| Ultra long-acting insulins (basal insulin) are usually taken between meals and at bedtime. |
Insulin degludec (Tresiba)Insulin glargine (Toujeo) |
Clear |
1 hour (up to 6 hours for insulin glargine) |
36–42 hours |
Mixtures of insulin can sometimes be combined in the same syringe, for example, intermediate-acting and rapid- or short-acting insulin. Not all insulins can be mixed together.
For convenience, there are premixed rapid- and intermediate-acting insulins. These come in a premixed ratio, such as 75/25, 70/30, and 50/50. For example, 75/25 means the mixture is 75% intermediate-acting insulin and 25% rapid-acting insulin. They are usually taken 2 times a day at the start of a meal. These insulins look cloudy. The insulin will start to work as quickly as the fastest-acting insulin in the combination. It will last as long as the longest-acting insulin. Examples include:
- Insulin regular and insulin NPH.
- Insulin lispro and insulin lispro protamine.
- Insulin aspart and insulin aspart protamine.