Insulin glargine
The first once-daily basal insulin analogue, and the first insulin to get an interchangeable biosimilar
Insulin glargine is engineered to be barely soluble at body pH, so it forms a depot under the skin and releases slowly over about a day. Approved as Lantus in 2000, it is now also sold as Toujeo, Basaglar and Semglee, the first interchangeable biosimilar insulin in the United States.
What is it?
Insulin glargine is acidic in the vial and comes out of solution when it meets the body's pH, forming a microprecipitate under the skin that dissolves slowly. The Lantus label describes the result: a slower, more prolonged absorption with a relatively constant profile over 24 hours and no pronounced peak, unlike NPH insulin.
Its original trial, in 518 people with type 2 diabetes, is the one that set the pattern for the class: equal control, less night-time hypoglycaemia, less weight gain than NPH insulin. A concentrated version, 300 units/mL (Toujeo), releases more slowly still; pooled trials found less hypoglycaemia in type 2 diabetes than with the 100 units/mL form, at the cost of needing more units.
Degludec, which lasts longer, is its main rival. Against glargine 300 the two were similar for HbA1c and lows in pooled open-label trials. Against glargine 100 in people prone to night-time lows, glargine showed an early-morning dip that degludec did not. Degludec given only three times a week, though, lowered HbA1c less than daily glargine. And a weekly GLP-1 drug has beaten it head to head.
Glargine has also found a hospital role. Given early alongside the insulin drip in diabetic ketoacidosis, it shortened resolution in one adult trial and cut rebound high glucose and treatment failure in children, though it did not speed resolution in the paediatric trial.
Insulin glargine is also where biosimilar insulin began in the United States. Basaglar arrived in 2015 and Semglee became the first interchangeable biosimilar insulin in 2021, and switching studies have found no loss of control.
The label is for improving blood-sugar control in adults and children with diabetes. It is given under the skin once daily, at any time of day but the same time each day, and it is not recommended for treating diabetic ketoacidosis. It must not be diluted or mixed with another insulin, and glucose should be watched closely when switching to it.
Mechanism of Action
Insulin glargine precipitates under the skin and dissolves slowly, giving a flat, day-long basal insulin.
pH-triggered precipitation
Soluble at acidic pH in the vial; forms a microprecipitate at body pH that dissolves gradually.
No pronounced peak
Relatively constant concentration over 24 hours (Lantus label 12.3).
Insulin receptor
Once released it acts like insulin, mainly controlling fasting glucose.
Published Research
These are the trials in people, read from their PubMed abstracts, with dosing and design from the Lantus label read on October 1, 2026.
The trial that established it
Five hundred and eighteen people with type 2 diabetes were randomised to once-daily insulin glargine or once- or twice-daily NPH for 28 weeks. HbA1c improved equally (−0.41% against −0.59%), while night-time hypoglycaemia was 25% lower after titration (26.5% against 35.5%, p = 0.014) and weight gain was smaller (0.4 kg against 1.4 kg, p < 0.0007).
Beaten by a weekly GLP-1 drug
In SUSTAIN 4, across 196 sites in 14 countries, once-weekly semaglutide was compared with once-daily insulin glargine added to metformin. Semaglutide produced greater reductions in HbA1c and weight with fewer hypoglycaemic episodes. Nausea was the common complaint on semaglutide (21-22%), nasopharyngitis on glargine (12%).
Switching to a biosimilar in practice
In 225 adults across five clinics converted from Lantus to Basaglar, the mean daily basal dose was unchanged at six months (46.3 against 45.9 units, p = 0.52), as was HbA1c at every time point. The estimated monthly cost was lower ($286 against $341 at conversion, p < 0.001).
Immune response to a biosimilar
In two phase 3 studies in 808 Chinese patients with type 1 or type 2 diabetes, detectable anti-insulin antibodies, antibody levels and treatment-emergent responses were similar for the biosimilar and for Lantus, and antibody status was not associated with control, dose, hypoglycaemia or safety.
Night-time glucose against degludec
In type 1 diabetes prone to nocturnal lows, glargine 100 produced a glucose dip at 4 a.m. and more variability; degludec gave a flatter profile and fewer nocturnal lows below 3.0 mmol/L (hazard ratio 0.36).
Children with ketoacidosis
In 82 children with diabetic ketoacidosis, adding glargine early did not speed resolution but cut rebound high glucose (risk ratio 0.57) and treatment failure (0.14).
Adults with ketoacidosis
In adults with diabetic ketoacidosis, early glargine (100 or 300 units/mL) alongside the insulin infusion shortened resolution to about 6.5 hours against 11.1 in controls and lowered the total insulin dose.
300 units/mL against 100 units/mL
Across 15 randomised trials, the concentrated 300 units/mL form caused less nocturnal and total hypoglycaemia than 100 units/mL in type 2 diabetes, but needed a higher basal dose in both type 1 and type 2.
Glargine 300 against degludec
Pooling four open-label trials of 2,727 people, glargine 300 and degludec gave similar HbA1c and hypoglycaemia; degludec lowered fasting glucose a little more. The evidence was rated very low certainty.
Against degludec three times a week
In three trials of 1,171 insulin-naive people with type 2 diabetes, degludec given three times weekly lowered HbA1c 0.27% less than daily glargine.
Dosing Data
Lantus is injected under the skin once daily at the same time each day, with the dose individualised and titrated to fasting glucose.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the Lantus label (SPL version 35, effective June 2, 2025).
Contraindications & Cautions
From the label.
Legal Status
An approved insulin with several products and biosimilars.
Frequently Asked Questions
?How does insulin glargine last all day?
It is formulated acidic and precipitates when it meets the body's pH, forming a depot under the skin that dissolves slowly. The label describes a relatively constant profile over 24 hours with no pronounced peak.
?When should it be injected?
The label says once daily, at any time of day, but at the same time every day, under the skin of the abdomen, thigh or upper arm, with sites rotated.
?What is the advantage over NPH insulin?
In the original 518-person trial, equal control with 25% less night-time hypoglycaemia and about a kilogram less weight gain.
?Are the biosimilars equivalent?
In a real-world switch of 225 patients, dose and HbA1c were unchanged and cost was lower; in 808 patients, antibody responses were similar. Semglee is designated interchangeable in the United States.
References
- [fda-pi] Lantus (insulin glargine) prescribing information, sections 1, 2, 4, 5, 6 and 12.3 (DailyMed SPL version 35, effective June 2, 2025; read October 1, 2026).
- [pubmed] Rosenstock J, et al. "Basal insulin therapy in type 2 diabetes: 28-week comparison of insulin glargine (HOE 901) and NPH insulin." Diabetes Care, 2001;24(4):631-6. PMID: 11315821.
- [pubmed] Aroda VR, et al. "Efficacy and safety of once-weekly semaglutide versus once-daily insulin glargine as add-on to metformin (with or without sulfonylureas) in insulin-naive patients with type 2 diabetes (SUSTAIN 4): a randomised, open-label, parallel-group, multicentre, multinational, phase 3a trial." Lancet Diabetes Endocrinol, 2017;5(5):355-366. PMID: 28344112.
- [pubmed] Pitlick JM, et al. "Real-World Evaluation of Dosing in Patients Converted From Insulin Glargine (Lantus) to Insulin Glargine (Basaglar)." Ann Pharmacother, 2020;54(9):846-851. PMID: 32037850.
- [pubmed] Wang W, et al. "Immunogenicity of LY2963016 insulin glargine and Lantus® insulin glargine in Chinese patients with type 1 or type 2 diabetes mellitus." Diabetes Obes Metab, 2022;24(6):1094-1104. PMID: 35187770.
- [pubmed] Joshi SR, et al. "Comparative clinical efficacy and safety of insulin glargine 300 U/ml (Toujeo) versus insulin glargine 100 U/ml in type 2 diabetes and type 1 diabetes: A systematic literature review and meta-analysis." Diabetes Obes Metab, 2023;25(6):1589-1606. PMID: 36748186.
- [pubmed] Alhmoud EN, et al. "Efficacy and safety of insulin glargine 300 units/mL vs insulin degludec in patients with type 1 and type 2 diabetes: a systematic review and meta-analysis." Front Endocrinol (Lausanne), 2023;14:1285147. PMID: 38313835.
- [clinical-trial] Brøsen JMB, et al. "Effect of insulin degludec versus insulin glargine U100 on nocturnal glycaemia assessed by plasma glucose profiles in people with type 1 diabetes prone to nocturnal severe hypoglycaemia." Diabetes Obes Metab, 2023;25(6):1557-1565. PMID: 36749303.
- [pubmed] Kamrul-Hasan ABM, et al. "Thrice-Weekly Insulin Degludec Versus Once-Daily Insulin Glargine in Insulin-Naïve Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis." Br J Hosp Med (Lond), 2025;86(7):1-16. PMID: 40705560.
- [clinical-trial] Bansal D, et al. "Insulin glargine supplementation during early management phase in children with diabetic ketoacidosis: a double-blinded randomised controlled trial." Arch Dis Child, 2025;110(12):983-987. PMID: 40623843.
- [clinical-trial] El Feky AY, et al. "Effectiveness and Safety of Early Insulin Glargine U100 and Glargine U300 Administration in the Management of Diabetic Ketoacidosis in Adults With Type 1 Diabetes Mellitus: A Randomized Clinical Trial." Endocr Pract, 2025;31(12):1554-1559. PMID: 40840711.
- [fda-pi] Lantus (insulin glargine injection) US prescribing information (DailyMed set 3a97c40f, effective July 22, 2023), sections 2.1-2.4; read through openFDA October 6, 2026.
Sources & Citations
Studies were read from their PubMed abstracts; the Lantus label from DailyMed through openFDA (set 3a97c40f) and the version read October 1, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.