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Thyroid Hormone (T3)

Liothyronine Sodium (T3)

Brand names: Tertroxin, Thybon Henning

Used in: Thyroid Disorders

Liothyronine is synthetic triiodothyronine (T3), a fast-acting thyroid hormone with a shorter duration of action than levothyroxine. It is reserved for specialist situations such as severe hypothyroidism or myxoedema coma, and is not routinely preferred over levothyroxine for maintenance.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Administer liothyronine sodium tablets orally once daily and individual dosage according to patient response and laboratory findings ( 2.1 ) See full prescribing information for recommended dosage for hypothyroidism ( 2.2 ) TSH suppression in well-differentiated thyroid cancer ( 2.3 ) and for thyroid suppression test ( 2.4 ) When switching a patient to liothyronine sodium tablets, discontinue levothyroxine therapy and initiate liothyronine sodium tablets at a low dosage. Gradually increase the dose according to the patient's response ( 2.5 ) Adequacy of therapy determined with periodic monitoring of TSH and T3 levels as well as clinical status ( 2.6 ) 2.1 General Principles of Dosing The …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-03-15. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It is the active thyroid hormone (T3) and acts directly on nuclear thyroid receptors to regulate metabolism, bypassing the peripheral conversion of T4 to T3 required for levothyroxine.

Prescribing in practice

  • Use with caution in cardiac disease, as it can provoke angina or arrhythmia; introduce and titrate carefully under specialist supervision.
  • Its rapid onset and shorter half-life make dosing less stable than levothyroxine, so it is not routinely preferred for maintenance.
  • Initiation and ongoing use for hypothyroidism should usually be directed by a specialist (e.g. endocrinology).

Monitoring

Monitor clinical response and thyroid function; in those with cardiac disease watch for angina or palpitations during titration.

Counselling the patient

  • Report chest pain, palpitations or a fast or irregular heartbeat.
  • Do not change or stop the dose without specialist advice.

Evidence & guidelines

Specialist-initiated; not routinely recommended over levothyroxine for primary hypothyroidism (NICE NG145).

Reference: BTA/BTAC Guidelines on Hypothyroidism 2019; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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