Can I take Ferrous and Levothyroxine together?

Why this happens

Iron binds to the levothyroxine in your stomach or gut, forming a 'complex' that is too large for your body to absorb into the bloodstream. Instead of working, the medicine simply passes through your system.

What you should do

You should separate these two medicines by at least 4 hours. 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. Your doctor may want to check your thyroid levels (TSH) more frequently if you start or stop taking iron.

Important precautions

Drug interaction (Timing)

You must separate these doses by at least 4 hours. Iron supplements (ferrous) stop levothyroxine from being absorbed, which can make your thyroid treatment ineffective.

Accidental overdose in children

Iron tablets are a leading cause of fatal poisoning in children. Keep them strictly out of reach, as even a small number of tablets can be lethal to a child.

Food and drink warnings

Tea and Coffee (Caffeine)

The tannins in tea and caffeine in coffee significantly reduce the amount of iron your body can absorb. Avoid drinking these for at least 1 to 2 hours before or after taking your iron supplement.

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 foods or drinks.

Eggs and Whole Grains

Compounds called phytates (in whole grains) and phosphates (in eggs) can hinder iron absorption. Try to space these foods away from your dose.

Coffee (Caffeine)

Coffee can significantly reduce the absorption of levothyroxine. You should wait at least 30 to 60 minutes after taking your tablet before drinking coffee.

Soya products

Soya can interfere with the absorption of levothyroxine. If you eat a lot of soya, your doctor may need to monitor your hormone levels more closely.

Grapefruit juice

Grapefruit juice may slightly delay the absorption of levothyroxine, though this is less critical than the timing of food in general. Consistency is key.

General Food Timing

Both of these medicines are best absorbed on an empty stomach. Crucially, iron and levothyroxine interact with each other; you must space them at least 4 hours apart, as iron prevents levothyroxine from working.

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.