People with type 1 diabetes must take insulin to regulate blood sugar levels. Different types of insulin are available that take effect at different speeds and last for varying lengths of time. Basal insulin is a slow-acting type.

The bodies of people with type 1 diabetes cannot produce enough insulin to control blood sugar. Every person who has type 1 must monitor their blood glucose and take insulin at different points during the day.

However, many people now use an electronic pump to provide different types of insulin at various points in the day, such as after meals. These act at different speeds to reduce blood glucose.

Type 2 diabetes reduces the ability of the cells to respond to insulin and absorb glucose, or blood sugar, leaving too much circulating the bloodstream.

People with type 2 more commonly use dietary control and regular physical exercise to manage blood glucose rather than insulin. They might take non-insulin medications, such as metformin. Some people with this type will need insulin if lifestyle measures and non-insulin medications are not effective.

In this article, we explain basal insulin, its effects, the different types, and how much to take.

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Basal insulin is slow-acting and regulates blood glucose between meals.

Basal insulin acts slowly and is important for people managing type 1 diabetes. Some people with type 2 might also need the hormone.

Different types of insulin are available. Manufacturers class them in the following ways:

  • onset time, or how quickly they work
  • duration, or how long their effects last
  • peak time, or when the effects of the insulin will peak

Planning is key when managing blood sugar with insulin. Timing and type are extremely important. After meals, a person needs a quick-acting insulin for rapid effects that counter the sudden surge in blood glucose.

Between meals and overnight, slower-acting insulin is necessary to give blood sugar a less extreme drop over a longer period while no new glucose enters the body. Slow-acting insulin is also known as basal insulin and plays a vital role in diabetes management during fasting.

During these times, the body continuously releases glucose into the bloodstream, which provides energy to the cells.

Basal insulin helps glucose control. The insulin reaches the bloodstream several hours after injection.

It keeps glucose levels constant throughout the day and night. In general, basal insulin remains in the system for up to 24 hours, although some have shorter or longer cycles in the body.

All types of basal insulin are long-acting.

A doctor might prescribe this type of insulin for types 1 and 2 diabetes. It generally acts in the body for up to 24 hours, although some varieties can last longer than this.

Depending on the type of insulin used and patient needs, a person should inject long-acting basal insulin either once or twice daily.

Long-acting insulin tends to have no peak activity and mimics the natural function of the pancreas. It allows for consistent delivery, keeping blood sugar levels steady throughout the day and night.

There are three different long-acting insulins.


Glargine is available as three different products: Basaglar, Lantus, and Toujeo.

These have the following characteristics:

  • They provide consistent activity from around 1 hour after injection.
  • They work for up to 24 hours.
  • A person will usually need to inject glargine once per day.


Pharmacies sell detemir under the brand name Levemir. Detemir has the following qualities:

  • It provides constant activity from within 1 hour of injection.
  • Detemir usually does not last as long as glargine, with a mean duration of around 7.6–24 hours.
  • A person requires 1–2 daily shots of detemir.


Insulin degludec, also on sale as Tresiba, provides consistent activity for more than 42 hours and allows for a more flexible injection schedule.

Be sure to allow 8 hours between doses of degludec.

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A doctor will personalize an individual’s insulin dosage.

Many factors help a doctor decide when and how often a person should use basal insulin.

These include:

  • lifestyle factors, such as activity level and diet
  • the body’s insulin needs
  • the individual’s willingness to inject, although insulin pumps can help reduce the need for frequent injections
  • blood sugar levels in the morning

Doctors base slow-acting insulin dosage on an individual’s needs and the type of diabetes they have. There is no single dosage for all people with either type of diabetes.

It is always important to discuss individual factors with a doctor and stick to their advice.

Type 1 diabetes

People with type 1 diabetes need to replace all of the body’s insulin. The pancreas does not produce any insulin whatsoever.

As such, people with type 1 diabetes should get their dose through an automatic, electronic insulin pump or by following a regimen that combines long- and short-acting insulins.

Talk to a doctor about the available options and find a regimen that suits your lifestyle.

Type 2 diabetes

Doctors usually recommend a slow-acting insulin program for people who have type 2 diabetes once non-insulin medications are no longer sufficient. They will base dosage on the individual’s weight, hormone levels, and diet.

However, a person with type 2 diabetes may be able to control the condition without taking insulin at all.

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Basal insulin presents a small risk of causing low blood sugar.

Basal insulin is central to many types of insulin therapy and offers several benefits, including:

  • Easier blood sugar level management: Levels remain more even, as basal insulin has no peak time.
  • More flexible lifestyle: People can vary meal and injection time more without affecting blood sugar control, also due to the lack of peak time.
  • Less frequent injections: People only require one to two injections of basal insulin per day.
  • Lower risk of complications: If a person uses basal insulin soon after receiving a diagnosis, the risk of severe complications reduces, according to one study from 2015.
  • Use as part of a basal-bolus regimen: A basal-bolus regimen combines long- and short-acting insulins, supplementing regular basal shots with an extra shot of bolus, or short-acting, insulin at meal times. However, it is more common nowadays for people to use a pump system.

However, there are also some disadvantages to using it, including:

  • Hypoglycemia: This is a common side effect of any insulin. While basal insulin presents a low risk, it is still present.
  • Night-time hypoglycemia: This might also be a possibility when using intermediate-acting insulin, as it keeps working overnight.
  • Weight gain: This is a possible effect of using any insulin.

Learn more about the best sites on the body for administering insulin injections here.

Basal insulin is one type of insulin. A person might combine other types with this treatment depending on the doctor’s advice.

Other types of insulin that can help manage symptoms of diabetes are:

Intermediate-acting insulin

People use this in the same way as long-acting insulin but generally need injections twice daily. Intermediate-acting insulin is also known as isophane or NPH insulin.

Its action peaks an average of 6.5 hours later, after which point the effect starts to reduce.

People often combine intermediate-acting insulin with short-acting or regular insulin in various ratios as part of a diabetes treatment plan.

Rapid-acting insulin

This begins to act within 15 minutes of administration and peaks at around 1 hour. These are most useful directly after meals.

Rapid-acting insulin might remain in the body for up to 4 hours. Types of rapid-acting insulin include:

  • lispro
  • glulisine
  • aspart

Short-acting or regular insulin

Short-acting or regular insulin begins to take effect in 30 minutes and peaks in approximately 2 to 4 hours.

Types of regular insulin include:

  • humulin R
  • novolin R

If you have diabetes, speak to your doctor about whether insulin supplementation is a necessary part of managing your blood sugar.

Basal insulin is a slow-acting type of insulin. People take it between mealtimes and before bedtime to control blood sugar outside of eating.

There are three types of basal insulin currently available: Glargine, detemir, and degludec. Pharmacies sell these under different brand names.

Some people use long-acting insulin in combination with shorter-acting insulins for the most effective glycemic control.

Basal insulin allows for an easier injection schedule, more flexible lifestyle, and a lower risk of complications. However, it can lead to hypoglycemia and weight gain.

Speak to your doctor about choosing the best type of insulin for you.

Learn about basal-bolus insulin therapy here.


How do I know if I need insulin?


If you have type 2 diabetes and are unable to reduce your blood sugar with diet, exercise and other non-insulin medications you may be a candidate for insulin use. You will need to work closely with your doctor to determine the best options for you.

Alan Carter, PharmD Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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