Can I take Levothyroxine and Simvastatin together?

Why this happens

Thyroid hormones influence how the body processes cholesterol and how it metabolises statin medications. An underactive thyroid can lead to higher levels of fats in the blood and may slow down the breakdown of simvastatin in the body.

What you should do

You can take these medicines together, but ensure your doctor monitors your thyroid stimulating hormone (TSH) levels regularly. If your levothyroxine dose is changed, your doctor may also want to check your cholesterol levels or monitor you for any new muscle aches or pains.

Important precautions

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.

Pregnancy

You must not take simvastatin if you are pregnant or planning to become pregnant, as it may harm the developing baby. Use effective contraception while taking this medicine.

Muscle disorders (Myopathy/Rhabdomyolysis) - simvastatin

You must report any unexplained muscle pain, tenderness, or weakness to your doctor immediately. This is especially important if you also feel unwell or have a fever, as it can lead to serious kidney damage.

Grapefruit and Grapefruit Juice

You must avoid eating grapefruit or drinking grapefruit juice while taking simvastatin. Grapefruit contains compounds that increase the level of simvastatin in your blood, which significantly increases your risk of serious side effects, such as muscle damage (rhabdomyolysis).

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 while taking levothyroxine. While there is no direct chemical reaction, alcohol can affect thyroid function and may worsen symptoms like tiredness or mood changes.

It is best to avoid or strictly limit alcohol when taking simvastatin. Both alcohol and simvastatin can affect your liver; combining them increases the risk of liver damage and may also increase the risk of muscle side effects.

Timing of dose and food/drink

Take your levothyroxine on an empty stomach, at least 30 to 60 minutes before breakfast or any caffeine. Food, milk, and coffee prevent the medicine from being absorbed properly.

Caffeine (Coffee/Tea)

Caffeine can significantly reduce the amount of levothyroxine your body absorbs. You should wait at least 30 to 60 minutes after taking your tablet before drinking coffee or tea.

Dairy products (Milk, Yoghurt, Cheese)

Avoid consuming dairy products at the same time as your levothyroxine. Calcium found in dairy can interfere with how your body absorbs the medicine, making it less effective. It is best to wait at least 4 hours between taking levothyroxine and consuming dairy.

Soya products

Soya can interfere with the absorption of levothyroxine. If you regularly eat or drink soya products, your doctor may need to monitor your thyroid levels more closely. Avoid consuming soya at the same time as your dose.

Kelp and Seaweed

These foods are naturally high in iodine. Too much iodine can interfere with your thyroid treatment and make your condition worse.

High-fibre foods

A diet very high in fibre 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.