Long-acting, or basal, insulin is a slow-acting type of insulin. It can help a person stabilize blood sugar levels throughout the day. Types of long-acting insulin include degludec, detemir, and glargine.

Insulin is a hormone that people with diabetes either cannot produce or do not efficiently use. However, those with the condition can supplement insulin with different types.

Fast-acting insulin replaces the surge of insulin that a healthy pancreas would release at mealtime. In contrast, long-acting insulin mimics the low-level flow of insulin that a healthy pancreas releases between meals and overnight.

Long-acting insulin works to establish a healthy baseline blood sugar level. This means that when food enters the body, blood glucose will increase from a lower and more regular point, making it easier to manage.

Many people now use an electronic insulin pump to deliver long-acting insulin without the need for manual injections. However, people who may not have access to a pump or choose not to use a pump for lifestyle reasons might still opt for injections.

In this article, we look at how to use the different types of long-acting insulin.

Long-acting insulin would not serve its purpose in pill form as the stomach would break it down during digestion.

Instead, people with diabetes should inject insulin into the fatty tissue under the skin.

From here, it gradually moves into the bloodstream.

There are different ways to inject insulin and different sites on the body that are safe to use.

Delivery methods

According to the National Institute of Diabetes and Digestive and Kidney Diseases, there are a few ways to deliver long-acting insulin. These include:

  • Pump: An electronic unit administers timed doses of long-acting insulin through a catheter, avoiding the need for regular injections.
  • Needle and syringe: The individual draws a dose of insulin from a vial using a syringe. They can then inject the insulin into a range of sites on the body. Avoid mixing different types of insulin in the same syringe.
  • Pen: A person can load a pen with a cartridge containing insulin and set the pen to deliver a premeasured dose. Alternatively, disposable pens are available that have prefilled levels of insulin.
  • Injection port: An injection port features a short tube that enters the tissue beneath the skin. An individual can deliver insulin through this port using either a syringe or pen. This only requires a skin puncture when the tube needs swapping.

A person can inject long-acting insulin under the skin of the abdomen, upper arms, or thighs.

Injections into the abdomen are the quickest route for insulin to reach the blood. The process takes a little more time from the upper arms and is even slower from the thighs.

It is important to stay consistent with the general injection area, but also to change the exact injection site frequently. Repeat injections at the same spot on the skin can cause lumps to form under the skin. This makes it harder for the insulin to work.

Each type of long-acting insulin has its own suggested dose. These vary depending on the type of diabetes and any history of insulin use.

When a person starts to use new insulin, the doctor will recommend that they begin with a smaller percentage of the target dose.

This gives the body time to adapt to the extra insulin. The doctor will then slowly start to increase the prescription to provide a full dose.

Adjustments to an insulin regimen may become necessary if there are changes to a person’s diet or daily physical activity levels or if a person becomes ill.

Any factors that can affect blood sugar might lead to a change in insulin dosage, as well as negative reactions to the hormone, such as weight gain.

Finding the ideal long-acting insulin regimen is a trial and error process that requires careful monitoring of blood sugar levels.

Learn more here about insulin pens, which often come with pre-prepared doses.

According to the American Diabetes Association, long-acting insulin differs from faster-acting insulins in three main ways:

  • Onset: This gives an idea of how long the insulin takes to work. Short and rapid-acting insulins start to lower blood sugar levels within 15 to 30 minutes. Long-acting insulin takes effect several hours after injection.
  • Peak time: This indicates the time at which a dose of insulin has its strongest effect. Rapid and short-acting insulins peak around 1–3 hours after injection. Long-acting insulin does not have a peak time. It works to regulate blood sugar levels at a fairly stable rate throughout the day.
  • Duration: This gives information on how long the effect of the insulins lasts. Faster-acting insulins can control blood sugar levels for only a few hours. Long-acting insulin can work for around 24 hours or longer, depending on the type of medication.

Long-acting insulin cannot stabilize post-meal blood sugar spikes. People with type 1 diabetes will often need to supplement their long-acting insulin regimen with faster-acting insulins when eating.

They may inject short- or rapid-acting insulin directly before eating.

When scientists create long-acting insulin, they change the structure of natural insulin. This is so that it can be absorbed into the bloodstream more gradually.

There are three forms of long-acting insulin currently on the market:

  • detemir
  • glargine
  • degludec

Below is a summary detailing how each of these work.


This insulin works over the course of the day.

  • Duration: 18– 24 hours
  • Administration: Inject detemir once or twice daily at the same time each day.
  • Brand name: Levemir


As an injection, insulin glargine forms clusters in the fatty tissue beneath the skin. These clusters break down slowly, gradually releasing small amounts of insulin into the bloodstream.

  • Duration: Up to 24 hours
  • Administration: Taken glargine once daily at the same time each day.
  • Brand names: Lantus, Basaglar, and Toujeo


This type of insulin works by slowing down the rate at which the bloodstream absorbs insulin molecules.

  • Duration: Up to 42 hours
  • Administration: Take once daily. With degludec, the timing does not need to be the same each day.
  • Brand name: Tresiba

A 2013 editorial in the journal Diabetes Therapy suggests that degludec works better than the older versions of long-acting insulin. However, because of pricing and health insurance coverage, insulin degludec is an expensive medication.

Speak to your doctor about an insulin that balances cost and individualized blood glucose requirements.