Levothyroxine
Also sold as: Euthyrox, Thyronorm, Eltroxin
Usual adult dose
Dose is set by your doctor and adjusted by blood tests; a usual adult starting dose is 25 to 100 micrograms once a day, lower in older people and heart patients. Take on an empty stomach, 30 to 60 minutes before breakfast, at the same time every day.
Your doctor may give you a different dose. Children's doses depend on weight.
Side effects
Common
- usually none at the right dose; too high a dose: fast heartbeat
- sweating
- shaking
- weight loss
- trouble sleeping
Serious — get help
Stop taking it and see a doctor straight away if you notice:
- chest pain
- very fast or irregular heartbeat
- severe allergic reaction
Do not take it, or take care, if
- Overactive thyroid that is not treated
- Recent heart attack or untreated adrenal problem
- Heart disease or older age (start with a low dose)
- Do not use for weight loss
Interactions
Medicines that can react with this one.
Moderate10 medicinesTake together only with care. Ask your doctor or pharmacist.
- Aluminium hydroxide + Magnesium hydroxide
Antacids reduce levothyroxine absorption; take them at least 4 hours apart.
- Calcium carbonate
Calcium reduces levothyroxine absorption; take them at least 4 hours apart.
- Calcium carbonate + Colecalciferol
Calcium reduces absorption of levothyroxine; take them at least 4 hours apart.
- Ferrous fumarate
Iron reduces absorption of levothyroxine; take them at least 4 hours apart.
- Ferrous sulfate
Iron reduces levothyroxine absorption; take them at least 4 hours apart.
- Ferrous sulfate + Folic acid
Iron reduces absorption of levothyroxine; take them at least 4 hours apart.
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- Multivitamin
Multivitamins with iron or calcium reduce levothyroxine absorption; take them at least 4 hours apart.
- Sodium alginate + Sodium bicarbonate
Can reduce levothyroxine absorption; take them at least 4 hours apart.
- Sucralfate
Sucralfate reduces levothyroxine absorption; separate doses by at least 4 hours.
- Warfarin
Starting or changing levothyroxine can increase the effect of warfarin; INR should be checked.
Minor3 medicinesUsually not a problem, but tell your doctor.
- Ispaghula husk
Fibre can reduce absorption; take levothyroxine at least 1 hour before.
- Omeprazole
Long-term omeprazole may reduce levothyroxine absorption; thyroid tests may need checking.
- Simeticone
Simeticone may reduce levothyroxine absorption; take them at least 4 hours apart.