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 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 strength is usually U-100 (or 100 units of insulin in one milliliter of fluid). Humulin R (regular) insulin is also available in U-500. This 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. Make sure you use the same type of insulin consistently. See the table below for types of insulin. footnote 1
Types of insulin
| Type |
Examples |
Appearance |
When it starts to work (onset) |
The time of greatest effect (peak) |
How long it lasts (duration) |
| Rapid-acting insulins (bolus insulin) work over a narrow, more predictable range of time. Because they work quickly, they are used most often at the start of a meal. They quickly drop the blood sugar level and work for a short time. |
Insulin aspart (Novolog), insulin lispro (Humalog), insulin glulisine (Apidra) |
Clear |
5–30 minutes |
30 minutes–3 hours |
3–5 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 |
10–15 minutes |
35-45 minutes |
1½–3 hours |
| Short-acting insulins take effect and wear off more quickly than long-acting insulins. A short-acting insulin is often used 30 minutes before a meal so that it has time to work. These liquid insulins are clear and do not settle out when the bottle (vial) sits for a while. |
Insulin regular (Humulin R U-100 and Novolin R) |
Clear |
30 minutes |
3 hours |
4–12 hours (U–100) |
| Intermediate-acting insulins contain added substances (buffers) that make them work over a long time and that may make them look cloudy. When these types of insulin sit for even a few minutes, the buffered insulin settles to the bottom of the vial. |
Insulin NPH (Humulin N and Novolin N) |
Cloudy |
1-3 hours |
4-12 hours |
Up to 24 hours |
| Long-acting insulins (basal insulin) work for a longer time to lower blood sugar levels throughout the day and night. |
Insulin detemir (Levemir), insulin glargine (Lantus and Basaglar), and insulin regular (Humulin R U-500) |
Clear |
60-90 minutes. 30 minutes for U-500 |
4-8 hours (U-500). No peak for other long-acting insulins |
Up to 24 hours |
| Ultra Long-acting insulins have no peak and last for 24 hours or more. |
Insulin degludec (Tresiba U-100 and U-200) and insulin glargine (Toujeo U-300) |
Clear |
6 hours (glargine). 1 hour (degludec) |
None |
Up to 36 hours (glargine). 42 hours or more (degludec) |
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 insulin. The insulin will start to work as quickly as the fastest-acting insulin in the combination. It will peak when each type of insulin typically peaks, and it will last as long as the longest-acting insulin. Examples include:
- 70% NPH and 30% regular (Humulin 70/30, Novolin 70/30).
- 50% lispro protamine and 50% lispro (Humalog Mix 50/50).
- 75% lispro protamine and 25% lispro (Humalog Mix 75/25).
- 70% aspart protamine and 30% aspart (NovoLog Mix 70/30).