Can I take Levothyroxine and Liothyronine together?

Why this happens

Both levothyroxine (T4) and liothyronine (T3) are synthetic versions of thyroid hormones. Levothyroxine is converted by the body into T3, while liothyronine is already the active form. Using both at the same time has an additive effect on your thyroid hormone levels.

What you should do

This combination is sometimes specifically prescribed by specialists (endocrinologists) for patients who do not feel well on levothyroxine alone. You should only take both if your doctor has explicitly told you to do so. Ensure you have regular blood tests to monitor your thyroid levels and report any symptoms like heart palpitations or excessive sweating to your GP.

Important precautions

Heart conditions (e.g. angina, heart failure, or recent heart attack)

These medicines increase the workload on your heart. If you experience chest pain, palpitations, or shortness of breath, you must contact your doctor immediately as your dose may need to be adjusted more slowly.

Diabetes

These medicines can raise blood sugar levels and may reduce the effectiveness of your diabetes medication. You must monitor your blood sugar more frequently when starting or changing your dose.

Adrenal gland insufficiency (untreated)

You must not start thyroid treatment until any adrenal gland problems are treated. Starting these medicines first can trigger a life-threatening medical emergency called an adrenal crisis.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking these medicines. Alcohol can interfere with how your thyroid hormones work and may worsen symptoms like tiredness or mood changes. Combining alcohol with thyroid medication can also increase the risk of liver strain.

Dairy products (Milk, Yogurt, Cheese)

Calcium found in dairy products can significantly interfere with the absorption of thyroid hormones. You should avoid consuming dairy within 4 hours of taking your medication.

Caffeine (Coffee, Tea)

Caffeine can reduce the amount of medicine your body absorbs. It is recommended to wait at least 30 to 60 minutes after taking your tablet before having a caffeinated drink.

Soya (Soybeans, Soy milk, Tofu)

Soya can interfere with how your body absorbs these medicines. If you eat a lot of soya, your doctor may need to monitor your thyroid levels more closely.

High-fibre foods

A very high-fibre diet (such as large amounts of bran or whole grains) can reduce the absorption of thyroid hormones. Try to keep your fibre intake consistent and discuss any major dietary changes with your doctor.

Papaya

Some studies suggest that eating papaya may interfere with the absorption of levothyroxine. It is best to avoid eating large amounts of papaya close to the time you take your dose.

Walnuts

Walnuts may reduce the absorption of thyroid medication. Avoid eating walnuts at the same time as taking your medicine.

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.