About levothyroxine sodium
Synthetic thyroid hormone
Used for
- Treats underactive thyroid (hypothyroidism)
- Helps suppress thyroid-stimulating hormone after some thyroid cancers
Usual adult dose
Usually taken once daily; dose is individualized and adjusted using blood tests. Replacement doses are often about 1.6 micrograms/kg daily in healthy adults under 50.
Usual dose in children
For congenital or acquired hypothyroidism, typically 10–15 micrograms/kg once daily in newborns, with lower age-based doses as children grow.
Common side effects
- Excess dosing may cause a fast or irregular heartbeat
- Tremor, nervousness, or trouble sleeping
- Increased sweating or heat sensitivity
- Weight loss or diarrhea
Important warnings
- Take consistently on an empty stomach, usually 30–60 minutes before breakfast.
- Separate from iron, calcium, and some antacids by at least four hours.
- Dose changes take weeks to show their full effect; blood tests guide adjustments.
- Use caution with heart disease, adrenal insufficiency, or severe untreated hypothyroidism.
Pregnancy
Usually continued during pregnancy; dose requirements often increase, so thyroid blood tests need closer monitoring.
Breastfeeding
Generally compatible with breastfeeding at prescribed doses.
Interactions
- Iron, calcium, antacids, and some foods can reduce absorption.
- Warfarin effects may increase when thyroid levels normalize.
- Some seizure medicines and rifampin can increase levothyroxine breakdown.
- Biotin supplements can distort thyroid blood test results.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.