Insulin glargine !
A long-acting insulin analogue: it forms tiny deposits under the skin and gives a steady, almost peakless basal level for about a day.
Updated 2026-11-01
The figure shows human insulin bound to site 1 of an insulin receptor fragment. Glargine (and its active metabolites) binds the same site; its changes affect absorption, not this contact.
Mechanism of action
Glargine differs from human insulin by a glycine at position A21 and two extra arginines at the end of the B chain. It is formulated as a clear acidic solution; at the neutral pH of the subcutaneous tissue it precipitates into micro-deposits that release insulin slowly and evenly. The released insulin activates the insulin receptor like human insulin, lowering glucose output by the liver and increasing uptake by muscle and fat.
- Clear acidic solution precipitates at the neutral pH under the skin
- Micro-deposits release insulin slowly, with no marked peak
- Activates the insulin receptor like human insulin
- Provides a steady basal level for about a day
Pharmacokinetics
- Absorption
- Subcutaneous; slow, prolonged absorption with a relatively constant level over 24 hours and no pronounced peak, unlike NPH.
- Metabolism
- Partly cleaved at the end of the B chain in the subcutaneous depot into two active metabolites with insulin-like activity.
- Onset and duration
- Long acting: starts slowly and lasts about a day, so it is usually given once daily at the same time.
Indications
- Basal insulin in type 1 diabetes, with mealtime insulin Type 1 diabetes mellitus →
- Basal insulin in type 2 diabetes, alone or with oral drugs Type 2 diabetes mellitus →
Adverse effects
Common
- Hypoglycemia (less nocturnal hypoglycemia than with NPH)
- Weight gain
- Injection-site reactions, lipodystrophy and localized cutaneous amyloidosis
- Low potassium
Contraindications
- During an episode of hypoglycemia
- Hypersensitivity to insulin glargine or an excipient
Key interactions
- Beta-blockers, clonidine
- Can blunt the warning signs of hypoglycemia.
- Other glucose-lowering drugs
- Raise the risk of hypoglycemia.
- Corticosteroids, diuretics, atypical antipsychotics, niacin
- Reduce the glucose-lowering effect.
- Thiazolidinediones (pioglitazone)
- Fluid retention and possible heart failure.
What is monitored
- Fasting blood glucose (guides basal adjustments)
- HbA1c
- Injection sites
Administration and safety
- Subcutaneous only: not given intravenously or in an insulin pump.
- Never diluted or mixed with any other insulin or solution in the same syringe.
- It is a clear solution like rapid insulins: the label is checked to avoid confusing basal and mealtime insulin.
- Pens, needles and syringes are never shared between patients.
Nursing care
- Before: fasting glucose and the time of the last basal dose.
- Give it at about the same time each day, even if the patient is not eating, unless the protocol says otherwise.
- Watch for hypoglycemia and rotate injection sites.
- Teach that glargine is not a correction insulin for a high reading.
Pregnancy and breastfeeding
Limited data have not shown a clear risk; it may be continued in pregnancy when it controls glucose well, with frequent monitoring.
Test yourself
Think of the answer, then tap the question to see it.
Why can glargine not be mixed with rapid-acting insulin in one syringe?
It is formulated at an acidic pH; mixing raises the pH, causes early precipitation and changes the action of both insulins.
What makes glargine almost peakless?
It precipitates into micro-deposits at the neutral pH of the subcutaneous tissue and dissolves slowly, giving a steady release.
A patient on glargine has repeated low readings at night. Which part of the regimen is checked first?
The basal dose: fasting and night readings mainly reflect basal insulin.
Related drugs
Related conditions
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Insulin Glargine (rDNA origin) Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - INSULIN GLARGINE- insulin glargine-yfgn injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 51 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.