About levothyroxine
Synthetic thyroid hormone replacement
Used for
- Treats severe hypothyroidism when oral treatment is not possible
- Treats myxedema coma
- Used with other treatment for certain thyroid cancers
Usual adult dose
For myxedema coma: typically 200–400 mcg intravenously once, then 1.6 mcg/kg daily; lower initial doses may be used for older adults or heart disease.
Usual dose in children
For severe hypothyroidism when oral treatment is not possible, doses are individualized by age and weight; specialist supervision is required.
Common side effects
- Fast or irregular heartbeat
- Chest pain
- Tremor or nervousness
- Excessive sweating or heat intolerance
Important warnings
- Intravenous treatment requires close medical monitoring.
- Excess dosing can cause serious heart problems.
- Use caution with heart disease, older age, or long-standing hypothyroidism.
- Not for weight loss or obesity treatment.
Pregnancy
Levothyroxine is generally continued in pregnancy; dose requirements may increase, and thyroid levels need monitoring.
Breastfeeding
Generally compatible with breastfeeding when taken at prescribed doses.
Interactions
- Calcium and iron can reduce absorption of oral levothyroxine.
- Warfarin effects may increase when thyroid hormone levels rise.
- Insulin and diabetes medicines may need adjustment.
- Some seizure medicines and rifampin can alter levothyroxine requirements.
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 It may be incomplete or out of date.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.