Long-Acting Insulin Analogue (Basal) Pregnancy: A large amount of data (>1000 pregnancy outcomes) indicates no specific adverse effect on pregnancy nor malformative or feto/neonatal toxicity; use may be considered during pregnancy if clinically needed. Insulin requirements may decrease during the first trimester and generally increase during the second and third; they decline rapidly immediately after delivery. Breast-feeding women may need insulin dose and diet adjustments.

Insulin Glargine

Brand names: Lantus, Toujeo (U300), Abasaglar (biosimilar)

Insulin glargine is a long-acting recombinant human insulin analogue used to provide basal glycaemic control in type 1 and type 2 diabetes mellitus.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Individualised (no fixed dose stated) - dose and timing adjusted to the patient

Route: Subcutaneous (must NOT be given intravenously)

Frequency: Once daily, at the same time each day

Long-acting basal insulin analogue (SPC: ABASAGLAR 100 units/mL); this variant shares the same posology as insulin-glargine. In type 2 diabetes may be combined with orally active antidiabetic agents. Potency is stated in units exclusive to insulin glargine (not the same as IU or units of other analogues). Intravenous administration of the usual subcutaneous dose could cause severe hypoglycaemia. Do not mix or dilute with any other insulin. Rotate injection sites (abdomen, deltoid or thigh) to reduce lipodystrophy/cutaneous amyloidosis. Not the insulin of choice for diabetic ketoacidosis (use intravenous regular insulin). Switching: from twice-daily NPH insulin reduce the daily basal dose by 20-30% during the first weeks; from insulin glargine 300 units/ml reduce dose by approximately 20% (products not bioequivalent/interchangeable). Paediatric: safety and efficacy established in children aged 2 years and older (dose and timing individually adjusted); not established below 2 years. Interaction list drawn from the US product label (BASAGLAR) as the captured UK SPC sections did not include section 4.5.

Dose adjustments

Renal

In renal impairment, insulin requirements may be diminished due to reduced insulin metabolism; in the elderly, progressive deterioration of renal function may lead to a steady decrease in insulin requirements.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to insulin glargine or to any of the excipients

Side effects

Hypoglycaemia (very common) - may be severe, recurrent episodes may cause neurological damage and may be life-threatening
Lipohypertrophy, lipoatrophy or cutaneous amyloidosis at the injection site (may delay local insulin absorption)
Injection site reactions; oedema
Allergic reactions (immediate-type rare; may include generalised skin reactions, angio-oedema, bronchospasm, hypotension and shock - may be life-threatening)
Visual impairment and retinopathy (marked change in glycaemic control may cause temporary visual impairment); dysgeusia; myalgia

Interactions

Drugs that may increase the risk of hypoglycaemia (may need dose reduction and more frequent glucose monitoring): other antidiabetic agents, ACE inhibitors, angiotensin II receptor blockers, disopyramide, fibrates, fluoxetine, MAO inhibitors, pentoxifylline, pramlintide, salicylates, somatostatin analogues (e.g. octreotide), sulfonamide antibiotics
Drugs that may reduce the blood-glucose-lowering effect (may need dose increase): atypical antipsychotics (e.g. olanzapine, clozapine), corticosteroids, danazol, diuretics, oestrogens, glucagon, isoniazid, niacin, oral contraceptives, phenothiazines, progestogens, protease inhibitors, somatropin, sympathomimetics (e.g. albuterol, adrenaline, terbutaline), thyroid hormones
Alcohol, beta-blockers, clonidine and lithium salts may increase or decrease the glucose-lowering effect; pentamidine may cause hypoglycaemia sometimes followed by hyperglycaemia; beta-blockers may mask hypoglycaemia warning symptoms

Clinical monograph

How it works

It binds insulin receptors to promote cellular glucose uptake and suppress hepatic glucose output; an amino-acid modification shifts its isoelectric point so it precipitates at physiological pH, giving a slow, relatively peakless absorption and prolonged duration.

Prescribing in practice

Hypoglycaemia is the principal hazard and may be more difficult to recognise when basal insulin is intensified or combined with other glucose-lowering agents.
Administer subcutaneously, usually once daily at a consistent time, and rotate injection sites to reduce the risk of lipohypertrophy.
Do not mix or dilute with other insulins, and be alert to differing strengths between glargine products to avoid dosing errors.

Monitoring

Monitor capillary blood glucose and HbA1c, adjusting the dose to the patient's glycaemic targets while watching for hypoglycaemia.

Counselling the patient

Always carry a fast-acting source of sugar and learn to recognise the warning signs of a low blood glucose.
Rotate injection sites within the same body region and never share insulin pens or needles.
Continue background insulin during illness and seek advice, as requirements may change.

Evidence & guidelines

Long-acting insulin analogues are established basal therapy in UK diabetes care and feature in NICE diabetes guidance.

Reference: NICE NG17 (T1DM); NICE NG28 (T2DM); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways