Insulins

Insulin glargine: Lantus, Basaglar, Semglee, Rezvoglar, Toujeo

insulin glargine · Long-acting (basal) insulin · Sanofi; Eli Lilly; Biocon/Viatris

✓Last reviewed · Written by Dr. George Grunberger · Medical review: pending — clinician review in progress · How we review

In short

Insulin glargine is a long-acting (basal) insulin made by Sanofi; Eli Lilly; Biocon/Viatris, used for basal blood sugar control in type 1 and type 2 diabetes. Schedule: once daily. It is prescription-only in the US and Canada.

FormVials, pens
How oftenOnce daily
United StatesFDA-approved. Semglee and Rezvoglar are interchangeable biosimilars to Lantus. Toujeo is a concentrated U-300 form. Levemir (insulin detemir) has been discontinued in the US.
CanadaAvailable in Canada (including biosimilars).
PrescriptionRequired

What it is used for

  • Basal blood sugar control in type 1 and type 2 diabetes

Insulin glargine dosage

Per the official label. Your prescriber sets your dose — never change it on your own.

Insulin glargine label dosing schedule
1DoseIndividualized in units, same time each day
2ToujeoU-300 concentration — not unit-for-unit identical to U-100 glargine when switching

How to take it

Under the skin once daily. Do not dilute or mix with other insulins.

Storage

Unopened: refrigerate. In use: Lantus up to 28 days; Toujeo up to 56 days.

How long it works compared with other insulins

How long each insulin type worksApproximate duration of action: rapid-acting about 4 hours, regular about 6 hours, NPH 12 to 18 hours with a peak at 4 to 12 hours, glargine about 24 hours, degludec up to 42 hours, icodec about one week.0 h12 h24 h36 h48 hRapid-acting (lispro, aspart, glulisine)Short-acting (regular)Intermediate (NPH)Long-acting (glargine)Ultra-long (degludec)Once-weekly (icodec)≈ 1 week →
Typical time-action profiles from product labels (darker band = peak). Your response can differ — follow your own plan.

Side effects

Common

  • Low blood sugar (hypoglycemia)
  • Injection-site reactions
  • Weight gain
  • Lipodystrophy or skin thickening at repeated injection sites

Serious — get medical help

  • Severe hypoglycemia (confusion, seizures, loss of consciousness)
  • Low potassium (hypokalemia)
  • Fluid retention and heart failure when combined with thiazolidinediones
  • Serious allergic reactions

Who should not use it

  • During an episode of low blood sugar
  • Never share pens or needles, even if the needle is changed
  • Do not switch insulin type, brand or concentration without your prescriber

Cost

Biosimilars and $35 programs lower costs.

GLP-1 cost without insurance →

How to buy Insulin glargine legally

  1. Get a prescription from your doctor or a licensed telehealth provider.
  2. Fill it at a licensed pharmacy.
  3. Verify any online pharmacy first (US: safe.pharmacy; Canada: your provincial pharmacy college register).

Buying legally in the USA → Buying legally in Canada →

Common questions

Frequently asked questions

What replaced Levemir?

After Levemir's US discontinuation, people were moved to other basal insulins such as glargine or degludec by their prescribers.

Also searched as: Lantus, Basaglar, Semglee, Rezvoglar, Toujeo, Lantus SoloStar, long-acting insulin, basal insulin, Levemir replacement, insulin glargine biosimilar

Sources

Checked against these primary sources on .

InsulinsInsulin degludec: Tresibainsulin degludec · Once dailyInsulinsInsulin icodec: Awiqli (once-weekly insulin)insulin icodec-abae · Once weeklyGLP-1 & incretin medicinesSoliqua 100/33insulin glargine + lixisenatide · Once daily
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