Rankings / Hormones & Endocrine

T3 (liothyronine)

Hormones & Endocrine · Active thyroid hormone

Tier B-

High-risk evidence profile

Reviewed by Read Off Label · Last reviewed · How we grade

thyroidprescriptionmitochondrial
High-risk evidence profile
6.2 / 10
Tier B-
Ev 8 Bn 8 Sf 3.5

Bottom line

Read Off Label grades T3 (liothyronine) as B- (6.2/10) based on strong evidence, high benefit magnitude, and a med-high-risk safety profile.

Its high-risk evidence profile reflects a Safety score of 3.5/10; reported benefits and harms can differ by indication, dose, route, duration, and population.

Often sought by patients who feel unwell on T4 monotherapy despite normal TSH.

Studied, labeled, or reported-use context: Clinical: 5-25 mcg/day, often divided, in T4/T3 combo therapy; supraphysiologic 25-100 mcg/day… — Rx; not individualized guidance.

What the evidence says

Often sought by patients who feel unwell on T4 monotherapy despite normal TSH. AACE/ATA 2014 guidelines acknowledge T3 combination therapy as reasonable. Short half-life (~1 day) typically requires divided dosing. Off-label fat-loss exposure (supraphysiologic 25-100 mcg/day) in euthyroid individuals is associated with endogenous thyroid suppression, muscle catabolism alongside fat loss, rebound hypothyroidism after discontinuation, cardiac arrhythmia, and bone loss.

Mechanism

Biologically active thyroid hormone; binds thyroid hormone receptors (TRα, TRβ); upregulates metabolic rate, lipolysis, protein turnover; shorter half-life (~1 day) than T4

Studied, labeled, or reported dose & route

Clinical: 5-25 mcg/day, often divided, in T4/T3 combo therapy; supraphysiologic 25-100 mcg/day reported in off-label fat-loss / bodybuilding contexts

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about T3 (liothyronine)'s effects?
Read Off Label rates the evidence for T3 (liothyronine) as Strong and the benefit magnitude as high, producing an overall grade of B- (6.2/10). Often sought by patients who feel unwell on T4 monotherapy despite normal TSH.
What safety findings are reported for T3 (liothyronine)?
T3 (liothyronine) has a med-high risk profile in the database. Med-High (atrial fibrillation, bone loss, cardiac stress; over-replacement thyrotoxicosis; abuse risk for weight loss) Legal status: Rx (Cytomel).
What does the low Safety score for T3 (liothyronine) represent?
The Safety score is 3.5/10. It records the substantial harms described for one or more use contexts; the Benefit score, indication, dose, route, duration, population, and legal status remain separate parts of the evidence profile.
What doses or routes are reported for T3 (liothyronine)?
Clinical: 5-25 mcg/day, often divided, in T4/T3 combo therapy; supraphysiologic 25-100 mcg/day reported in off-label fat-loss / bodybuilding contexts This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does T3 (liothyronine) work?
Biologically active thyroid hormone; binds thyroid hormone receptors (TRα, TRβ); upregulates metabolic rate, lipolysis, protein turnover; shorter half-life (~1 day) than T4

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.