Levothyroxine
Levothyroxine is a synthetic form of thyroxine (T4) — the primary thyroid hormone. It is the standard treatment for hypothyroidism (underactive thyroid) and is also prescribed after radioactive-iodine-treatment or thyroid surgery, which often result in hypothyroidism.
Absorption Interactions
Levothyroxine is best absorbed on an empty stomach. The following interfere with its absorption and should be taken at least four hours apart:
- soy and soy-containing foods
- calcium-rich foods and calcium supplements
- Iron supplements (ferrous sulphate)
- High-fibre foods (in large amounts)
biotin supplements do not affect levothyroxine itself, but distort thyroid blood test results — stop biotin for 2 days before testing.