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Insulin glargine

Brand names: Lantus, Basaglar, Toujeo, Semglee, Rezvoglar

Insulin glargine is a long-acting insulin that keeps blood sugar steady for about a day. It's used in type 1 and type 2 diabetes.

Brand namesLantus, Basaglar, Toujeo, Semglee, Rezvoglar
Type of medicineLong-acting insulin
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It's called basal or background insulin. It doesn't cover the rise in blood sugar after meals.

Different brands aren't always swapped unit for unit; follow your prescription.

What it's used for

  • Type 1 diabetes (with mealtime insulin)
  • Type 2 diabetes

How to take it

  • Inject it under the skin once a day at the same time each day.
  • Rotate injection spots within the belly, thighs, or upper arms.
  • Never mix it with other insulins in the same syringe.
  • Never share pens, even with a new needle.
  • Check your blood sugar as your provider tells you.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Low blood sugar
  • Weight gain
  • Redness or lumps where you inject
Call 911Severe low blood sugar: confusion, seizure, passing out, or can't swallow safely. Use glucagon if you have it, then call 911.
Call your provider todayFrequent low blood sugar, or readings that stay high
Call your provider todaySwelling in the legs or shortness of breath, especially with pioglitazone

Warnings

  • Know the signs of low blood sugar: shakiness, sweating, fast heartbeat, hunger, and confusion. Keep fast sugar with you.
  • Illness, skipped meals, alcohol, and extra exercise can cause lows.

Other medicines, foods, and alcohol

  • Other diabetes medicines add to the risk of low blood sugar.
  • Beta blockers can hide signs of low blood sugar.
  • Steroids and some other medicines raise blood sugar.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Insulin is used in pregnancy. Your needs often change, so work closely with your provider.

Missed doses, overdose, and storage

If you miss a dose

Ask your provider ahead of time what to do if you miss a dose. Check your blood sugar, and don't take two doses close together.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Keep unopened pens and vials in the refrigerator (don't freeze). Once opened, follow the label for how long it lasts at room temperature. Keep away from heat and sunlight.

Conditions it's used for

Sources

Last updated 2026-11-13.