What is long-acting insulin?

Long-acting insulin is insulin that stays working in your body the longest. Long-acting insulin typically reaches the bloodstream several hours after injection, though it may take only one to two hours for some people. The American Diabetes Association says long-acting insulin starts working four to six hours after injection, while other sources say it can start working as early as one hour after.

When does long-acting insulin peak and how long is it active?

This insulin lowers your blood sugar levels fairly evenly throughout the whole day, and it is designed to have minimal peaks, meaning moments when it is at its maximum strength in lowering blood sugar. It is most effective 10 to 18 hours after injection. Long-acting insulin works for about 24 hours.

When should I take long-acting insulin?

Long-acting insulin is best used as a background insulin throughout your day instead of just at mealtimes like rapid-acting and short-acting insulin. You can inject your full dose of this long-acting insulin all at once to cover the next 24 hours, or half of your daily dose can be taken every 12 hours, depending on your doctor’s recommendations.

Which products should I look for?

Long-acting insulin brands include:
- insulin glargine (Lantus), lasts up to 24 hours
- insulin detemir (Levemir), lasts 18 to 23 hours
- insulin glargine injection (Toujeo), lasts more than 24 hours
- insulin degludec injection (Tresiba), lasts up to 42 hours

Anything else I should know?

Patients prescribed long-acting insulin may also be prescribed rapid-acting or short-acting insulin.

Learn more about insulin:

Everything You Need to Know About Rapid-Acting Insulin
Everything You Need to Know About Short-Acting Insulin
Everything You Need to Know About Intermediate-Acting Insulin