Basal Insulin for Type 2 Diabetes

Medically Reviewed by Michael Dansinger, MD on April 09, 2022
4 min read

You can manage type 2 diabetes several ways, including with a healthy diet and regular exercise. But sometimes, you may need insulin and other medication to help control your blood sugar levels. The two main ways to take insulin are bolus and basal.

Bolus insulin is the quick-acting delivery that you often take before mealtimes. Basal insulin is longer-acting and helps keep your glucose levels steady day and night.

Generally, your total daily dosage of injected insulin is split between these short- and longer-acting kinds.

You may also hear it called background insulin. That’s what “basal” means. Your pancreas normally makes set amounts of insulin around the clock. Basal insulin mimics that process, and your body absorbs it slowly and uses it throughout the day.

You need less insulin when you’re not eating, but everyone needs a steady flow of it.

If you’ve been diagnosed with type 2, your doctor may start you on basal insulin. One shot a day may be enough. If not, your doctor may recommend adding more rapid-acting bolus “meal” insulin just before or after you eat.

Most basal insulin is injected into the fat just under your skin. You can do that with a needle and syringe to draw the right amount of medication. You also can use prefilled disposable pens that many people find easier to use.

Basal insulin is delivered in three main types. They differ on how soon they start working (onset), how long they last, and when the insulin’s effects peak in your body.

Your doctor may prescribe a mix of insulin types for use throughout the day, depending on how much your blood sugar rises and falls, and on your lifestyle.


NPH (Humulin N, Novolin N). This can start working as quickly as an hour or two. It reaches its maximum effect in 4-12 hours and stays in your body for up to 24 hours.


Detemir (Levemir) and glargine (Basaglar, Lantus). These take about 2 hours to get into your bloodstream. Effects last about 24 hours. Long-acting basal insulin doesn’t really hit a peak. That can help match how your body would release insulin if it were able to.


Degludec (Tresiba) and glargine u-300 (Toujeo). These start to work in 1-6 hours. They can last 36 hours or more. Ultra-long-acting insulin doesn’t peak. That means its effect stays even instead of rising and falling.

A big advantage with basal insulin is that you need only one or two shots a day, sometimes less often, compared to bolus “meal” insulin. It also gives you more flexibility when and where you can eat, since you don’t need to time your injections to mealtimes or carry your insulin around.

Studies found that long-acting glargine may control blood sugar as well as short-acting and intermediate-acting insulin does, but with fewer shots and at lower amounts.

Ultra-long-acting insulins also may better prevent your blood sugar level from falling too far, especially overnight when you’re fasting. Hypoglycemia is a major concern with insulin therapy. It can trigger heart problems and even death.

Long-acting insulins can be more expensive than other types. That could be a concern especially if you don’t have insurance coverage.

Your doctor will help you calculate how much insulin you need. The basic formula is based on your weight.

Insulin concentration is measured in units per milliliter of liquid. Your starting dose is based on your weight. You and your doctor may have to adjust that by 2-4 units at a time during the following days until you find the dose that works best for you. You and your doctor may fine-tune the dose as time passes.

Insulin is safe and rarely causes problems. The most common side effects are:

  • Low blood sugar (hypoglycemia). One way this can happen is if you get too much insulin for the amount of blood sugar in your body at a given moment. Low blood sugar can make you feel tired, shaky, cranky, and sweaty. It also can make your heart beat irregularly.
  • Weight gain. Insulin helps the blood sugar from your food more easily get into the cells to burn as energy. But if you get more calories than your body needs, the extra glucose in the cells is stored and turn into fat.
  • Allergic reaction at the site of the shot