Key takeaways:
Long-acting insulin and rapid-acting insulin are both commonly used to treat diabetes. The main differences between long-acting insulins and rapid-acting insulins are how fast and how long they work.
Long-acting insulins take a few hours to start working. They can provide a steady level of insulin in your body for a full day or even longer.
Most rapid-acting insulins start working within 15 to 30 minutes. They can help prevent blood glucose (sugar) spikes after meals.
Most long-acting insulins are injected once a day. But there is a weekly insulin that only needs to be injected once every 7 days. Rapid-acting insulins are injected a few times per day around meals.
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Insulin is an important treatment for many people living with diabetes. Some insulins are long-acting, some are rapid-acting, and some are in between.
If you’re living with Type 1 diabetes, injecting insulin is essential. This is because your body can’t make insulin, which leads to high blood glucose (sugar). Injecting insulin brings your blood sugar down to safe levels. People living with Type 1 diabetes usually use a combination of long-acting and rapid-acting insulins.
If you’re living with Type 2 diabetes, you may not need to inject insulin. But it’s a helpful (and sometimes necessary) treatment for many with the condition. This is because Type 2 diabetes is caused by the body not making enough insulin and/or not responding normally to insulin (also called insulin resistance). People living with Type 2 diabetes usually start with a long-acting insulin if needed. A rapid-acting insulin may be added later on.
So what’s the difference between long-acting and rapid-acting insulin? Below are the main differences and a few other things you should know.
What is long-acting insulin?
Long-acting (basal) insulin provides a slow, steady release of insulin. This type of insulin works throughout the day and night to balance your blood sugar between meals and when you’re asleep. Many long-acting insulins are injected once a day. There’s also a once-weekly insulin that you only need to inject every 7 days.
Long-acting insulin names
Many people are familiar with the brand-name versions of insulins. Sometimes, there are two or more brand names for a specific insulin.
Common names of long-acting insulins include:
Key features of long-acting insulin
The table below highlights the key features of the different long-acting insulins.
| Insulin glargine | Insulin degludec | Insulin icodec | |
|---|---|---|---|
| Brand names |
|
|
|
| FDA-approved conditions |
|
|
|
| Approved age range |
|
Ages 1 and older | Ages 18 and older |
| When it starts working |
|
1-2 hours | 6 hours |
| Peak levels | No peak | No peak | No peak |
| How long it lasts | 24 hours | More than 40 hours (almost 2 days) | At least 7 days |
| How often you inject doses | Once a day | Once a day | Once a week |
How much time does it take for long-acting insulin to work?
Long-acting insulins have different onset times. (“Onset time” is the term for how long it takes a medication to start working.) Here’s how their onset times compare:
Basaglar: 3-4 hours
Lantus: 3-4 hours
Rezvoglar: 3-4 hours
Semglee: 3-4 hours
Toujeo: 6 hours
Tresiba: 1-2 hours
Awiqli: 6 hours
Long-acting insulin usually does not “peak,” meaning that there are steady levels of insulin in your body throughout the day.
How long does long-acting insulin last?
Long-acting insulin products work for different amounts of time, or have different “durations of action.” Here is the typical duration of action for each long-acting insulin:
Basaglar: 24 hours
Lantus: 24 hours
Rezvoglar: 24 hours
Semglee: 24 hours
Toujeo: 24 hours
Tresiba: more than 40 hours
Awiqli: at least 7 days
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Should you inject long-acting insulin at bedtime?
For some people, injecting insulin at bedtime makes it easier to remember. But there’s no consensus on what time of day is best to inject long-acting insulin. And it may vary from person to person.
Injecting your insulin at the same time every day (for once-daily insulin) is more important than the exact time of day you inject it. With once-weekly insulin, you don’t need to be consistent about the time of day you inject it. Just make sure you inject it on the same day each week.
What’s the longest-lasting insulin?
Awiqli is currently the longest-lasting insulin on the U.S. market. Its effects last for 7 days. That means you only need to administer it once a week. Another weekly insulin, insulin efsitora alfa, could be approved in the near future. This insulin also lasts for 7 days in the body.
What is rapid-acting insulin?
Rapid-acting insulin is usually injected before, during, or after a meal. This type of insulin can help prevent blood sugar spikes after eating.
Examples of rapid-acting insulins are:
How long does it take for rapid-acting insulin to start working?
Onset times vary between rapid-acting insulin products:
Admelog: 15-30 minutes (peak levels after 30 minutes - 2 hours)
Afrezza: about 12 minutes (peak levels after 35-55 minutes)
Apidra: 12-30 minutes (peak levels after 1.5 hours)
Fiasp: 5 minutes (peak levels after 30 minutes)
Humalog: 15-30 minutes (peak levels around 30 minutes - 2 hours)
Kirsty: 15 minutes (peak levels after 1-3 hours)
Lyumjev: 15-30 minutes (peak levels around 30 minutes - 2 hours)
Merilog: 15 minutes (peak levels after 1-3 hours)
NovoLog: 15 minutes (peak levels after 1-3 hours)
Rapid-acting insulins last about 2 to 6 hours.
Do you need more than one insulin?
Some people living with diabetes, such as certain people with Type 2 diabetes, may only need to use a long-acting insulin to manage their blood sugar levels. Others, especially those living with Type 1 diabetes, may need a combination of rapid-acting and long-acting insulins.
If you’re using an insulin pump, you’ll likely only need a rapid-acting insulin. The pump gives you a slow and steady amount of insulin to cover you all day. But you may want to ask your prescriber if you should have an emergency supply of long-acting insulin in case your pump fails. Insulin pumps are more common for people living with Type 1 diabetes than those with Type 2 diabetes.
Your prescriber can determine the best insulin types and dosages for you.
Is there anything in between rapid-acting and long-acting insulin?
Yes, there are short-acting and intermediate-acting insulins available. Regular insulin (Novolin R, Humulin R) is an example of a short-acting insulin. Neutral protamine hagedorn (NPH) insulin (Novolin N, Humulin N) is an example of an intermediate-acting insulin.
Short-acting insulins are used similarly to rapid-acting insulins to reduce blood sugar spikes after eating. But they take a bit longer to start working (30 to 60 minutes). And they last a bit longer (about 5 to 8 hours).
Intermediate-acting insulins are used similarly to long-acting insulins: They manage blood sugar elevations when rapid-acting or short-acting insulins finish working. Because their effects peak about 4 to 10 hours after injection, they can be helpful if you experience overnight blood sugar spikes. But they last for a shorter period of time than long-acting insulins — or about 8 to 16 hours — so they’re typically injected twice a day.
What are combination insulins?
Some insulin products combine fast-acting and intermediate-acting insulins. The two types of insulin work together to help manage blood sugar spikes after eating, between meals, and at night. You typically inject combination insulin products twice daily.
Here are a few examples of combination insulins:
Insulin lispro protamine and insulin lispro (Humalog 50/50, Humalog 75/25)
Insulin aspart protamine and insulin aspart (NovoLog 70/30 Mix)
NPH insulin and regular insulin (Humulin 70/30, Novolin 70/30)
Frequently asked questions
No, Mounjaro (tirzepatide) isn’t an insulin. It’s a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. It’s approved for Type 2 diabetes. Mounjaro stimulates your pancreas to release natural insulin when you eat. It also signals your liver to make less sugar.
The directions for handling a missed dose vary between long-acting insulins. It’s best to ask your healthcare team if you’re unsure.
If you use a daily, long-acting insulin, such as Lantus, ask your prescriber how to manage missed doses. In some cases, they may recommend injecting a missed dose. Other times, they may suggest skipping it and just waiting until your next scheduled injection.
If you use a weekly insulin, such as Awiqli, you can inject a forgotten dose if it’s been less than 4 days since you missed it. If it’s been 4 days or more, just skip the missed dose and wait until your next scheduled injection.
Daily, long-acting insulin doesn’t need to be given at night. But for some people, injecting at night makes it easier to remember.
You can inject daily, long-acting insulin anytime of day that’s convenient for you. Just make sure to inject your dose at the same time every day. This helps provide consistent benefits.
No, Mounjaro (tirzepatide) isn’t an insulin. It’s a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. It’s approved for Type 2 diabetes. Mounjaro stimulates your pancreas to release natural insulin when you eat. It also signals your liver to make less sugar.
The directions for handling a missed dose vary between long-acting insulins. It’s best to ask your healthcare team if you’re unsure.
If you use a daily, long-acting insulin, such as Lantus, ask your prescriber how to manage missed doses. In some cases, they may recommend injecting a missed dose. Other times, they may suggest skipping it and just waiting until your next scheduled injection.
If you use a weekly insulin, such as Awiqli, you can inject a forgotten dose if it’s been less than 4 days since you missed it. If it’s been 4 days or more, just skip the missed dose and wait until your next scheduled injection.
Daily, long-acting insulin doesn’t need to be given at night. But for some people, injecting at night makes it easier to remember.
You can inject daily, long-acting insulin anytime of day that’s convenient for you. Just make sure to inject your dose at the same time every day. This helps provide consistent benefits.
The bottom line
Long-acting and rapid-acting insulin can both be helpful for managing diabetes. Long-acting insulin takes a few hours to start working. But it provides a steady level of insulin in your body throughout the day. Most rapid-acting insulins start working within 15 to 30 minutes. They can help prevent blood glucose (sugar) spikes after meals.
Most long-acting insulins are injected once a day. But there is a weekly insulin that only needs to be injected once every 7 days. Rapid-acting insulins are injected a few times per day around meals.
Your healthcare team will work with you to determine whether long-acting, rapid-acting, or a combination of both is right for you.
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References
American Diabetes Association. (n.d.). Insulin basics for diabetes.
American Diabetes Association Professional Practice Committee for Diabetes. (2026). 9. Pharmacologic approaches to glycemic treatment: Standards of Care in Diabetes—2026. Diabetes Care.
Centers for Disease Control and Prevention. (2024). Types of insulin.
Mannkind. (2026). Afrezza - insulin human powder, metered, Afrezza - insulin human kit [package insert]. DailyMed.
Merck Manual Professional Version. (n.d.). Onset, peak, and duration of action of human insulin preparations.
Porcellati, F., et al. (2014). Pharmacokinetics and pharmacodynamics of insulin glargine given in the evening as compared with in the morning in Type 2 diabetes. Diabetes Care.
Rosenstock, J., et al. (2025). Weekly fixed-dose insulin efsitora in Type 2 diabetes without previous insulin therapy. The New England Journal of Medicine.
Xu, K., et al. (2026). Insulin icodec: A once-weekly basal insulin on the horizon for diabetes management with implications for hospital care transitions. Health Sciences Review.
Yau, M., et al. (2021). Treatment of diabetes mellitus in children and adolescents. Endotext.
