What it’s for
- Replacement treatment for hypothyroidism
Synthetic T4 thyroid hormone, usually taken orally.
Purpose, evidence and practical considerations.
It is an established treatment for thyroid-hormone deficiency. Taking extra hormone with normal thyroid function does not provide a safe weight-loss or anti-ageing strategy.
Confidence: strong
The boxed warning states thyroid hormones should not be used for obesity or weight loss. Excess replacement can cause arrhythmia, bone loss and hyperthyroid symptoms. Absorption is affected by food, calcium, iron and many medicines, so timing and monitoring must be individualized.
Levothyroxine replaces thyroxine, which is converted in tissues to active triiodothyronine and regulates gene expression, growth and metabolism. Effects and dose requirements change slowly because of its long half-life.
Regulatory status: FDA-approved prescription thyroid-hormone replacement
The evidence on this page does not automatically apply to:
How people use it, with their schedules, context and original sources.
100 mcg · Daily
diagnosed hypothyroidism at age 21
Dose and schedule patterns reported in public protocols; these are observations, not prescribing advice. Private and hidden usage is excluded.
daily
These share a protocol with this intervention. This does not establish that they work together or are suitable alternatives.