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Insulins · Endocrine

Insulin glargine

basal insulin · Lantus® · Basaglar® · Toujeo®(brand names vary by market)

The flat background insulin that covers the fasting state.

View the class Practise
Illustration of Insulin glargine as a pen injectorINS

Also: injection

Mechanism

A modified insulin that precipitates at the neutral pH of subcutaneous tissue and dissolves slowly, giving a near-peakless profile over roughly a day.

Indications

  • Type 1 diabetes
  • Type 2 diabetes needing insulin

Formulations

Pen injectorInjection

Dosing concepts

What it is titrated against

Basal insulin is titrated against the FASTING morning glucose and nothing else. Adjusting it because of a high post-meal reading is the classic error and produces overnight hypoglycemia.

Concentration

Different products of the same molecule exist at different concentrations and are not interchangeable unit for unit by pen.

Never stopped in type 1

Basal insulin continues during illness and fasting, sometimes at a reduced dose. Stopping it is how ketoacidosis begins.

Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.

Pharmacokinetics

Half-life
Effective duration around 24 h, longer for the concentrated product
Elimination
plasma: Degraded peripherally; renal impairment prolongs insulin action generally and lowers requirements

No pronounced peak, which is what distinguishes it from NPH and reduces nocturnal hypoglycemia.

Play with these concepts in the PK Lab

Adverse effects

  • Hypoglycemiacommon & serious
  • Weight gaincommon
  • LipohypertrophycommonFrom injecting the same spot repeatedly; absorption from a lumpy site is erratic and is a hidden cause of unexplained variability.
  • Injection-site reactioncommon

Contraindications & precautions

Contraindications

  • Hypoglycemia at the time of administration

Precautions

  • Renal or hepatic impairment, which lower requirements
  • Changing brands or concentrations
  • Illness and fasting

Interactions

Monitoring

Fasting capillary glucose

The number this insulin is titrated against

Hypoglycemia frequency, timing and awareness

Nocturnal lows are the ones patients do not report

Injection sites

Lipohypertrophy explains a great deal of unexplained glucose variability · At every review, by looking and feeling

HbA1c

Overall control

Counselling points

  • Same time each day; rotate your injection sites systematically.
  • Never stop your basal insulin, even if you are not eating. Contact us instead.
  • Store spare pens in the fridge; the one in use stays at room temperature for the stated period.
  • Always carry fast-acting glucose.
  • Do not change brands without speaking to us: they are not always the same strength.

Clinical pearls

  • Rising fasting glucose with lows at 3am is over-basalisation, not under-treatment. Increasing the dose makes it worse, and only a nocturnal reading reveals it.
  • Injecting into lipohypertrophy is one of the most common and most invisible causes of erratic control; the fix is free and takes thirty seconds to teach.

References & review

  • Insulin glargine product monograph (consult the current version for your market) (monograph)
  • Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)

Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.

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