Liothyronine
Liothyronine is a synthetic form of the thyroid hormone triiodothyronine (T3), one of the body's primary metabolic hormones. It is prescribed to treat hypothyroidism (underactive thyroid), myxedema coma, and certain thyroid cancer conditions. The medication works by directly supplying the active T3 hormone to restore normal metabolic function in patients whose thyroid glands do not produce adequate hormones.
Liothyronine is a thyroid hormone replacement medication used to treat underactive thyroid conditions by supplementing the body's natural T3 levels.
This medication carries a boxed (black box) warning — the strongest type of FDA warning. Review the full prescribing information before use.
Key facts at a glance
- RxNorm
- 10814
- Generic
- Liothyronine
- Class
- unclassified
- Brands
- Liomny, Cytomel, Thyrolar
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- injection, tablet
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Primary uses include treatment of hypothyroidism, myxedema coma, and thyroid cancer. It may also be used in combination with levothyroxine (T4) therapy for some patients with hypothyroidism who do not respond adequately to T4 alone.
Liothyronine (T3) enters cell nuclei and binds to thyroid receptor proteins attached to DNA. This hormone-receptor complex controls DNA transcription and protein synthesis, directly increasing cellular metabolic activity throughout the body.
Requires careful dosing as it has a rapid onset of action. Should be used cautiously in patients with cardiovascular disease, elderly patients, and those with adrenal insufficiency. Regular thyroid function monitoring is essential. Not appropriate for weight loss in patients with normal thyroid function.
Official drug label
WellAlly may earn a referral fee from linked resources at no extra cost to you. Editorial content is never influenced by commercial relationships.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy