NZ Formulary



What does it do?

Levothyroxine is a thyroid hormone. It is used if your thyroid gland does not make enough thyroid hormone.

Before you start

  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

How should you take it?

Take levothyroxine regularly as directed with a glass of water.

What if you forget a dose?

Take the missed dose as soon as possible and continue as directed.

Can you take other medicines?

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

  • products containing aluminium, calcium, iron or magnesium, such as antacids (e.g. Mylanta®) or multivitamins

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Symptoms of a fast or irregular heartbeat including: fluttering, pounding or pain in your chest, dizziness or fainting

Feeling hotter than normal, sweating

Nervousness, restlessness, tremor, trouble sleeping

Diarrhoea, weight loss

Hair loss or thinning

Changes in periods

Tell your doctor - they may need to change your dose.

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

Important information continues on next page.

Other information:

  • You will need regular blood tests while you are taking levothyroxine to make sure you are on the right dose.
  • Levothyroxine should not be used for weight loss.