insulin glargine
long-acting insulin analogue· Brands: Lantus, Toujeo, Basaglar, Semglee, AbasaglarSC
Mechanism of action
Insulin glargine is a recombinant human insulin analogue with structural modifications that delay its absorption. It binds to insulin receptors and activates downstream signalling pathways, promoting peripheral glucose uptake, inhibiting hepatic glucose production, and suppressing lipolysis and proteolysis. The modifications cause the insulin to precipitate at physiological pH, forming a slowly absorbed subcutaneous depot that provides a relatively constant, peakless insulin concentration for approximately 24 hours.
Pharmacokinetics
After subcutaneous injection, insulin glargine is slowly and continuously absorbed from the depot, yielding a prolonged, peakless plasma profile. Its onset of action is about 1 to 2 hours, and the duration of action is up to 24 hours or longer. The bioavailability is roughly 60 to 80%, but this may vary with injection site. Metabolism is similar to human insulin, with degradation products excreted in the urine and bile. The apparent half-life is prolonged due to slow absorption, but there is no significant accumulation with once-daily dosing.
Indications & dosing
Type 1 diabetes mellitus
Basal insulin; commonly started at 0.2-0.4 units/kg once daily, individually titrated. Usually combined with rapid-acting insulin for meals.
- adult · SC: 0.2–0.4 units/kg once daily · Basal insulin; commonly started at 0.2-0.4 units/kg once daily, individually titrated. Usually combined with rapid-acting insulin for meals.
Type 2 diabetes mellitus
Initial dose often 10 units once daily, adjusted based on fasting glucose. Alternatively, weight-based 0.2 units/kg.
- adult · SC: 10 units once daily · Initial dose often 10 units once daily, adjusted based on fasting glucose. Alternatively, weight-based 0.2 units/kg.
Contraindications & precautions
- Hypoglycaemia · Insulin would exacerbate existing hypoglycaemia.
- Hypersensitivity to insulin glargine or any excipient · May cause severe allergic reactions.
- Use with caution in renal or hepatic impairment; dose reduction may be needed.
- Do not use to treat diabetic ketoacidosis; use a short-acting insulin.
- Do not mix with other insulins or dilute; administer subcutaneously only.
- Rotate injection sites to reduce risk of lipodystrophy.
- Monitor blood glucose regularly and adjust dose during illness or stress.
- Caution with drugs that may affect glucose levels, such as corticosteroids or beta-blockers.
Adverse effects
- Hypoglycaemiaserious
- Weight gain
- Injection site reactions
- Lipodystrophy
- Hypokalaemiaserious
- Allergic reactionsserious
Monitoring, pregnancy & toxicity
- Blood glucose · Regular monitoring, especially during dose titration and when changing insulin
- HbA1c · Every 3–6 months
- Hypoglycaemia symptoms · At each review
- Injection site reactions · At each review
- Serum potassium · Baseline and periodic, particularly if risk of hypokalaemia
- Renal and hepatic function · Periodically, especially in elderly or those with comorbidities
- Pregnancy: Insulin glargine may be used during pregnancy; however, data are limited compared with NPH insulin. Insulin requirements often change during pregnancy, so frequent glucose monitoring and dose adjustment are essential. It is a suitable alternative to NPH insulin if the patient is already stabilised on glargine or if it is the local formulary choice.
- Toxicity: Hypoglycaemia: sweating, tremor, confusion, palpitations, loss of consciousness · Treat with oral glucose if conscious; give IV dextrose or IM/SC glucagon if severe or unconscious. Because of the prolonged action, monitor blood glucose closely for 24–48 hours and consider admission.
Antidotes & reversal
- Dextrose 10-50% IV · Prolonged (up to 24 h+) hypoglycaemia risk - admit for dextrose infusion after correction.
Clinical notes
Insulin glargine is a long-acting basal insulin given once daily by subcutaneous injection, at the same time each day. It is used in type 1 and type 2 diabetes mellitus, and may be used in combination with rapid-acting insulin or other antidiabetic agents. It is not suitable for intravenous use or for diabetic ketoacidosis, which requires short-acting insulin. It should not be mixed with other insulins, as this disrupts the depot. Hypoglycaemia is the main adverse effect, and the risk of nocturnal hypoglycaemia is lower than with NPH insulin. Dose is individualised and adjusted based on blood glucose monitoring. Various strengths and pen devices are available; always check the product name and concentration before prescribing. Follow local formulary guidance.
Log in to read the full insulin glargine monograph
A free account unlocks the complete drug reference, the interaction checker, prescription practice and every other learning tool.
BNF; local formulary