Liothyronine (T3) (Liothyronine Sodium (Cytomel))
The active thyroid hormone prescribed by telemedicine clinics for subclinical hypothyroidism, stubborn weight loss, and metabolic optimization. T3 is the biologically active form that directly controls metabolic rate.
How it works
Binds nuclear thyroid receptors to regulate gene transcription for basal metabolic rate, thermogenesis, protein synthesis, and carbohydrate/fat metabolism in virtually every tissue.
Key facts
- Molecular weight: 650.97 Da
- Half-life: ~2.5 days
- Bioavailability: ~95% oral
- Storage: Room temperature.
Dosing overview
- Typical dose: 5-25 mcg
- Frequency: Daily (split AM/PM)
- Duration: Ongoing with monitoring
- Route: Oral tablet or sustained-release capsule
Protocol notes
- Usually started very low (5 mcg) and titrated up slowly based on labs and symptoms.
- Often split AM/PM (or compounded as sustained-release) because plain T3 is short-acting.
- When added to T4 therapy, the T4 dose is sometimes reduced to keep the ratio balanced.
Reported benefits
- Metabolic rate increase
- Weight loss support
- Improved energy
- Better mood
- Reduced brain fog
- Enhanced fat oxidation
Possible side effects
- Heart palpitations
- Anxiety
- Insomnia
- Sweating
- Bone loss (high doses long-term)
Research
- Low-dose T3 in metabolic optimization (2022): Addition of 5-10mcg T3 to T4 therapy improved patient-reported energy and cognitive scores with stable TSH.
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Research and educational reference only. Not medical advice.