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What is long-acting insulin?

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How it worksWho it's forHow it's deliveredTypesSummary
Long-acting insulin is a type of insulin that slowly releases into your bloodstream and maintains your blood glucose at a constant and stable level for a long time. 
Medically reviewed by Philip Ngo, PharmD
Written by Suan Pineda
Updated on

Long-acting insulin is a type of insulin that takes longer to reach your bloodstream to lower your glucose. 

Also known as basal insulin, long-acting insulin can manage your blood sugar for an entire day, similar to how the insulin made by your pancreas works.

Long-acting insulin is suitable for people with type 1 and type 2 diabetes. Let’s look at how long-acting insulin works, the different types, and who should take it.

Why is long-acting insulin given?

person testing blood sugar
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Doctors prescribe long-acting insulin to keep your blood sugar levels at a moderate and stable range while sleeping and between meals. Ultra long-insulin takes longer to start working but lasts longer.

After an injection, it can take up to 2 hours for long-acting insulin to start working, but the effect can last up to 24 hours. Ultra long-acting insulin can take 6 hours to start working but can last up to 36 hours.

Long-acting and ultra long-acting insulin are different from other types of insulin.

Compared with fast-acting insulin, they:

  • take longer to take effect
  • last longer
  • don’t peak or cause extreme drops in glucose

Instead, the insulin slowly reaches your bloodstream and can remain in your system throughout the day and night to keep your blood glucose under control. 

Long-acting insulin is key for managing blood sugar levels and providing energy to the cells when sleeping, fasting, or between meals.

What are some other diabetes medications?

Who does it suit and who is it not suitable for?

Long-acting insulin is suitable for people with type 1 and type 2 diabetes.

People with type 2 diabetes may use long-acting insulin if lifestyle strategies and other treatments can’t help them manage their blood glucose levels.

People with type 1 diabetes need to take insulin because their pancreas doesn’t make it. Long-acting insulin helps them set a moderate baseline for their blood glucose levels.

This makes it easier to manage diabetes. For instance, when food enters the body, blood sugar levels will increase from a lower point. In this way, it enables a more constant glucose level.

Learn more about the differences between type 1 and type 2 diabetes. 

Can it treat a sudden change in glucose levels?

You can’t take long-acting insulin when you experience a sudden drop in blood glucose levels. For this, you’d need fast-acting insulin, which has a more immediate effect and can help increase your blood glucose to a moderate level sooner.

Can anyone use it? 

Certain types of long-acting insulin are not suitable during pregnancy.

Also, people who have the following conditions may not be able to use insulin therapy, or a doctor may adjust their doses:

  • renal impairment 
  • liver failure
  • hypoglycemic episodes
  • hypokalemia, or low potassium
  • a hypersensitivity to cresol, a preservative found in many insulin products

A doctor can advise you on which insulin drugs are best for you.

Side effects

Long-acting insulin drugs have side effects that include:

  • dizziness
  • rashes
  • muscle cramps
  • problems with breathing and swallowing
  • weakness
  • swelling of the lips, face, throat, hands, and feet

If you experience any of these effects, talk with your doctor. 

How is it delivered?

Long-acting insulin is usually delivered by injection through a needle or syringe once or twice a day

Other methods to deliver long-acting insulin include:

  • an electronic pump
  • an injection port
  • a pen loaded with an insulin cartridge

Most injections are given subcutaneously, or just under the skin. A person injects them in a place with fatty tissue, such as the stomach, thighs, hips, or back of the arms.

Types of long-acting and ultra long-acting insulin drugs

There are three types of long-acting and ultra long-acting insulin drugs:

  • Detemir (Levemir): This is a long-acting drug that replaces the insulin the pancreas usually produces and helps move sugar from your blood to other parts of your body. A doctor may prescribe a dose once or twice per day. Detemir is sold under the brand-name drug Levemir.
  • Glargine: This is another long-acting drug. It works similarly to detemir, by replacing the insulin usually produced by your body and moving sugar from your blood to other tissues. Glargine takes up to 2 hours to become effective and lasts up to 24 hours. It’s sold under the brand-name drugs Lantus, Toujeo, and Basaglar.
  • Semglee: This is a biosimilar or synthetic version of glargine. Synthetic versions are often cheaper than the original version. It takes 1.5–2 hours to start working and lasts up to 24 hours.
  • Degludec: Degludec (Tresiba) is ultra long-acting and can last up to 36 hours. For this reason, it offers more flexibility in terms of injection timing. It is suitable for both type 1 and type 2 diabetes.

People usually take long-acting insulin with other diabetes medications or other types of insulin. Your dosage and combination of medication are tailored to your specific case. Talk with your doctor about the best line of treatment for you.

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Long-acting insulin is a type of insulin that maintains your blood glucose level constant for a longer period of time.

This type of insulin can take several hours to reach the bloodstream, but it can keep your blood sugar stable for a whole day.

Healthcare professionals use long-acting insulin to treat people with type 1 and type 2 diabetes. There are three types of long-acting insulin — degludec, detemir, and glargine — sold under different brand names.

All types of insulin can cause adverse effects, such as dizziness, shortness of breath, and muscle cramps. Talk with your doctor if you experience these effects.

Download the free Optum Perks Discount Card to save up to 80% on some prescription medications.

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