Can I take Levothyroxine and Sertraline together?

Why does sertraline make levothyroxine less effective?

Sertraline can change how your body processes thyroid hormones. It may reduce the amount of free thyroid hormone available in your blood, meaning your current dose of levothyroxine might not be enough to keep your levels stable.

What you should do

You can take levothyroxine and sertraline together, but taking sertraline may make your levothyroxine less effective.

You should tell your doctor if you are starting, stopping, or changing your dose of sertraline. Your doctor may want to perform a blood test to check your thyroid levels (TSH) a few weeks after starting sertraline to see if your levothyroxine dose needs to be adjusted.

Important precautions

Depression and anxiety disorders

You may experience an increase in suicidal thoughts or the urge to self-harm when first starting sertraline or changing the dose. This is more common in young adults under 25. Contact your doctor or go to hospital immediately if you notice any changes in your mood or behaviour.

Bleeding disorders or use of blood thinners (e.g. warfarin, aspirin)

Sertraline can increase your risk of bleeding, particularly in the stomach. Seek medical help if you notice unusual bruising or black, tarry stools.

Low sodium levels (hyponatraemia)

Sertraline can cause a serious drop in blood sodium levels, especially in the elderly. Seek urgent care if you experience confusion, weakness, or unsteady gait.

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 while taking sertraline. Combining alcohol with this medicine can increase side effects like drowsiness, dizziness, and impaired coordination. It can also make your depression or anxiety worse.

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.

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.

Grapefruit juice

Grapefruit juice can increase the levels of sertraline in your blood, which may increase the risk of side effects. It is best to avoid drinking large amounts of grapefruit juice.

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.