skip to main content

What does it do?

Levothyroxine is used to add thyroid hormones to your body.

How should you take it?

Take levothyroxine regularly as directed with a glass of water. Take it on an empty stomach – one hour before or two hours after food.

What if you forget a dose?

Take the missed dose as soon as possible. If it is close to the time for your next dose, skip the missed dose and carry on as normal. Do not take two doses at the same time.

Can you take other medicines?

Some medicines available without a prescription may react with levothyroxine including:

  • antacids (e.g. Mylanta®), supplements containing calcium (e.g. Calci-tab®) or iron (e.g. Ferro-Tab®) - do not take these within four hours of levothyroxine.
  • iodine supplements (e.g. Iodine/Lugol’s solution®)

Tell your pharmacist or doctor about all medicines or treatments that you may be taking including vitamins, herbal products (e.g. kelp powder) or recreational drugs. Avoid foods such as seaweed or kelp that may contain iodine.

What side effects might you notice?

Side EffectsRecommended action

Chest pain, change in heartbeat


Heat intolerance, sweating

Restlessness, irritability, nervousness, tiredness

Hair loss or thinning

Changes in periods

Diarrhoea, nausea, vomiting, weight loss

Trouble sleeping

Tell your doctor

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • Tell your doctor if you have heart problems, diabetes, osteoporosis (weak bones), or high blood pressure.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • Levothyroxine should not be used for weight loss.

This leaflet contains important, but not all, information about this medicine.

Prepared by the PILs Committee at Christchurch Hospital, Canterbury District Health Board, New Zealand. September 2017

For more general information about this sheet annd its contents, see: What does a My Medicines sheet cover?

Web links for this sheet in different formats

Click on buttons to copy web addresses for this leaflet:

If your browser does not automatically copy these links use its copy command instead.

About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at the Canterbury District Health Board. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed