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.
Community reviews of Liothyronine (T3)
- growth_factor_gabe rated it 5/5 - Noticed clear benefits within weeks: Added Liothyronine (T3) to my protocol about 3 months ago and it has earned its place. The benefits became noticeable around week 2-3 and have been consistent since. What I appreciate about this compound is the predictability. It does what the research suggests it should do, at roughly the timeline you would expect. No surprises, no dramatic swings, just steady improvement. No notable side effects to report at my dose. Sourcing is always the challenge with research compounds, insist on third-party testing. Storage and reconstitution per standard protocols. Plan to continue.
- quiet_gains rated it 4/5 - Solid compound with real results: Been using Liothyronine (T3) for about 6 months and the results are clear. Not overnight dramatic, but a steady, consistent improvement that became undeniable by the end of the first month. The mechanism makes sense based on what I have read in the literature, and my subjective experience matches the expected timeline. Benefits built gradually and plateaued at a good level. Side effects were minimal to none at the dose I used. Followed proper protocols for sourcing, storage, and administration. Would recommend to others who have done their research and have realistic expectations.
- cycle_sage rated it 4/5 - Worth adding to the protocol: Liothyronine (T3) has been a worthwhile addition. I am data-driven and tracked relevant markers before, during, and after. The improvement is measurable and correlates with the intervention timeline. What sets this apart from some compounds I have tried is the consistency. Benefits did not fluctuate wildly or disappear. They built up and maintained. That gives me confidence in the mechanism. Tolerance has been excellent. Nothing in my bloodwork or subjective experience raised any flags. This is the kind of compound that does its job quietly without causing problems. Exactly what you want.
- subq_samantha rated it 5/5 - Consistent improvement over 6 weeks: Added Liothyronine (T3) to my protocol about 6 weeks ago and it has earned its place. The benefits became noticeable around week 2-3 and have been consistent since. What I appreciate about this compound is the predictability. It does what the research suggests it should do, at roughly the timeline you would expect. No surprises, no dramatic swings, just steady improvement. No notable side effects to report at my dose. Sourcing is always the challenge with research compounds, insist on third-party testing. Storage and reconstitution per standard protocols. Plan to continue.
- reid_f rated it 4/5 - the scale finally moved after months stuck: what got me was how my stubborn winter weight actually budged, nine pounds over six weeks without changing much else about my desk job routine. felt warmer too, which sounds weird, but the number on the scale was the real story for me here. rest was pretty minor.
- optimized_macros rated it 4/5 - Helped me cut the last stubborn kilos, but touchy stuff: I tried liothyronine after a rough stretch where my cutting phase just stalled, even with training and food tight. I’m a CrossFit coach, so I notice when my engine feels off. Over about 4 months I dropped 11 kg and, for me, the scale finally moved without me feeling like I was dragging a tyre. I did notice it could feel a bit too punchy if I pushed food too low, so I kept a close eye on it...
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Community discussions about Liothyronine (T3)
- Looking at the latest T3 info from the peptide database – what do you think? - 4 comments
- Ask the community about Liothyronine (T3)
Research and educational reference only. Not medical advice.