# T3 (Triiodothyronine)

*Also known as: Liothyronine, Cytomel, T3*

Liothyronine (T3); short half-life requiring divided dosing.

## Overview

T3 (liothyronine, Cytomel) is the active thyroid hormone, used for hypothyroidism and used off-label for fat loss in bodybuilding contexts despite the significant metabolic disruption it carries. It binds nuclear thyroid hormone receptors that regulate genes controlling basal metabolic rate, thermogenesis, and protein turnover, raising resting energy expenditure and accelerating carbohydrate and fat metabolism. The compound has a roughly 22-hour half-life, peaks within hours, and shows about 95% bioavailability, but its effects are tightly regulated by the hypothalamic-pituitary-thyroid axis, so exogenous dosing suppresses thyroid-stimulating hormone and can blunt endogenous production with prolonged use. Effects include increased metabolic rate and fat loss, while risks at supraphysiological doses are tachycardia, arrhythmia, muscle wasting, anxiety, osteoporosis, and a rebound hypothyroid state when discontinued. Harm reduction centers on confirming genuine hypothyroidism with full thyroid panel before use and understanding that thyroid suppression from exogenous T3 can persist for weeks after stopping.

## Pharmacokinetics

- **Model tier:** advanced
- **Half-life:** 0.9 days (22.0399999992 hours)
- **Cmax:** 6.92 ng/dL
- **Tmax:** 0.1 days
- **Bioavailability:** 95%

## Dosing

- **Default dose:** 0.025 mg
- **Typical range:** 0.025–0.075 mg
- **Units:** ng/dL

## Source

- **Label:** PMC T3 PK
- **URL:** https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5167556/

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**Canonical URL:** https://anabolicdex.com/compounds/t3-triiodothyronine
**Plot:** https://anabolicdex.com/plot?compound=t3-triiodothyronine