Levothyroxine is a hormonal medication usually used for the purpose of replacement or supplemental therapy in conditions of thyroid disorder. Learn how to use the medication, its common side effects, special precautions to watch out for, and more.

What is this medication for?

Levothyroxine is a hormonal medication usually used for the purpose of replacement or supplemental therapy in conditions of thyroid disorder.

How should I take this medication?

• Do not stop taking your medication without checking with your healthcare professional.
• Take Levothyroxine in the morning on an empty stomach, at least 30 minutes before the first food or drink of the day. You may take it with half a glass of water. 
• Avoid supplements containing calcium or iron, antacids, milk or dairy products within 2 to 4 hours of taking Levothyroxine as taking them together might decrease the absorption Levothyroxine into your body
• Take the medication at the same time every day to ensure that it always has the same effect. 
• Do not stop taking your medication or change the brand of levothyroxine without informing your doctor.

What should I do if I forget to take this medication?

• If you miss a dose of Levothyroxine, take it as soon as you remember. However if it is near your next dose, skip the missed dose and resume your usual dosing schedule.
• Do not double your dose to make up for a missed dose.​

What precautions should I take?

Inform your healthcare professional if you:

• have any other medical conditions e.g. heart problems such as angina and history/recent heart attack, high blood pressure
• are taking other medications, vitamins such as calcium, herbal products and other traditional medications, as some of them may affect the level of levothyroxine in your body 

What are some common side-effects of this medication?

​Generally, this medication has been well tolerated. Side effects usually have been mild and may goes away as the body adjusts to the medication. 

Common side effects include:

• Headache
• Nervousness
• Sweating
• Increased appetite
• Diarrhea
• Weight loss
• Difficulty sleeping/Insomnia

If you have any concerns regarding the side effects of Levothyroxine, discuss with your healthcare professional. Do not stop taking medication on your own.

What are some rare but serious side-effects that I need to seek medical advice immediately?

• Chest pain
• Fast or irregular heartbeat
• Shortness of breath
• Excessive sweating
• Fits/Seizures
• The symptoms of a drug allergy include one or more of the following: 
  • swollen face/eyes/lips
  • difficulty in breathing
  • itchy skin rashes over your whole body

If any of these happens, stop taking your medication and see a doctor immediately as you will need treatment straight away.

What food or medication should I avoid when I take this medication?

Avoid food, drinks, medications or supplements that are high in calcium, iron or magnesium 2 to 4 hours before and after taking Levothyroxine.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing it into the rubbish chute or bin.

Disclaimers

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated Jul 2022