Can I take Iron and Levothyroxine together?

Iron and levothyroxine should not be taken at the same time as taking them together can significantly reduce the amount of thyroid hormone your body absorbs.

Why this happens

Iron binds to levothyroxine in the stomach and intestines, forming a complex that is too large for the body to absorb into the bloodstream. This means the medicine passes through your system without working.

How to take iron and levothyroxine safely

• You should take these medicines at least 4 hours apart.

• Most people find it easiest to take their levothyroxine first thing in the morning (on an empty stomach) and wait until the afternoon or evening to take their iron supplement.

• Do not stop taking either medication without speaking to your doctor or pharmacist.

Important precautions

Accidental overdose in children

Iron supplements are a leading cause of fatal poisoning in children. Keep them strictly out of reach and sight of children; even a small number of extra tablets can be fatal to a child.

Heart conditions (e.g. angina, heart failure)

If you have a heart condition, your dose must be started very low and increased slowly. Contact your doctor immediately if you experience chest pain or palpitations, as levothyroxine increases the workload on your heart.

Interaction with supplements (Calcium/Iron)

Do not take calcium tablets, iron supplements, or multivitamins at the same time as levothyroxine. You must leave a gap of at least 4 hours between these supplements and your levothyroxine to ensure the medicine works.

Diabetes

Levothyroxine can raise blood sugar levels. If you have diabetes, you must monitor your blood glucose more closely when starting or changing your dose, as your diabetes medication may need to be increased.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol when taking these medicines. While there is no direct 'danger' interaction, alcohol can irritate the stomach lining (already a risk with iron) and may interfere with the consistency of your thyroid hormone levels.

Tea and coffee (caffeine)

Tea and coffee contain compounds called tannins and polyphenols that significantly reduce the amount of iron your body can absorb. Avoid drinking these for at least 1 hour before or 2 hours after taking your iron supplement.

Drinking coffee at the same time as taking your levothyroxine can significantly reduce the amount of medicine your body absorbs. Wait at least 30 to 60 minutes after taking your tablet before drinking coffee.

Dairy products (milk, cheese, yoghurt)

Calcium in dairy products prevents iron from being absorbed properly. Do not take your iron supplement at the same time as dairy products. Leave a gap of at least 2 hours.

Whole-grain cereals and eggs

Phytic acid in whole grains and certain proteins in eggs can hinder iron absorption. It is best to take iron on an empty stomach, though you can have a small amount of fruit or vitamin C-rich juice to help absorption.

Soya (soy)

Soya can interfere with how levothyroxine is absorbed by the body. If you eat a lot of soya, your doctor may need to monitor your hormone levels more closely. Try to keep your soya intake consistent and avoid eating it close to the time you take your tablet.

Kelp and seaweed

These foods are very high in iodine. Because levothyroxine is a thyroid hormone, high levels of iodine can interfere with your treatment and make your thyroid overactive or underactive.

Using other medicines

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.