Can I take Anastrozole and Levothyroxine together?

Why this happens

Anastrozole (used for breast cancer) and levothyroxine (used for an underactive thyroid) are processed by different pathways in the body. They do not interfere with each other's absorption, metabolism, or excretion, nor do they have opposing or overlapping effects on the body's systems.

What you should do

You can continue to take both medications as prescribed by your doctor. It is usually best to take levothyroxine on an empty stomach, first thing in the morning, at least 30 to 60 minutes before breakfast or taking other medications like anastrozole, to ensure it is absorbed properly. Always inform your doctor if you notice any new symptoms or changes in your health.

Important precautions

Pregnancy and Breastfeeding

You must not take anastrozole if you are pregnant or breastfeeding, as it can cause serious harm to the developing baby. If you are pre-menopausal, you must use effective non-hormonal contraception (such as condoms) during treatment.

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.

Calcium or Iron Supplementation

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

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

Food (General)

Levothyroxine should be taken on an empty stomach, at least 30 to 60 minutes before breakfast or any caffeinated drinks. Food can significantly interfere with how much medicine your body absorbs.

Caffeine (Coffee/Tea)

Coffee and tea can reduce the absorption of levothyroxine. You should wait at least 60 minutes after taking your tablet before drinking coffee or tea.

Dairy products (Milk/Yoghurt)

Calcium found in dairy products can bind to levothyroxine and prevent it from being absorbed properly. Avoid consuming dairy within 4 hours of taking your dose.

Soya

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 and adjust your dose.

Dietary Fibre

A very high-fibre diet can reduce the absorption of levothyroxine. If you significantly change your fibre intake, inform your doctor as your dose may need adjusting.

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.