Taking this common thyroid medicine? Experts warn against drinking coffee too soon afterwards

For many people, the morning routine is almost automatic: take a tablet, head to the kitchen and switch on the coffee machine. If you take medication for an underactive thyroid, however, there is one part of that routine worth paying attention to.

The timing of your first cup of coffee can matter more than you might expect. Dutch medicine leaflets and thyroid patient organisations specifically mention coffee in their advice, and research has investigated why the two should not be taken together. The good news is that a small adjustment to your morning routine may help you avoid the problem.

Why coffee can interfere with thyroid medication

Levothyroxine is a synthetic version of the thyroid hormone thyroxine (T4). It is prescribed to people whose thyroid does not produce enough hormone, including those who have had their thyroid removed.

For the treatment to work properly, your body needs to absorb the medicine consistently. That's why levothyroxine tablets are usually taken on an empty stomach with a glass of water.

Coffee is one of the drinks that can interfere with this process. The Dutch patient organisation SchildklierNL specifically lists coffee among the things that can reduce levothyroxine absorption. Soy products and foods containing large amounts of dietary fibre can also affect how much of the medicine your body takes in.

What did the Italian study discover?

Researchers led by Salvatore Benvenga investigated the connection between coffee and levothyroxine in a study published in the journal Thyroid in 2008.

The researchers examined six patients and nine healthy volunteers. They compared what happened when participants took levothyroxine with water, with coffee, or with water followed by coffee an hour later.

The results showed that drinking coffee at the same time as the tablet reduced the average rise in thyroid hormone levels in the blood. The reduction was around 36% in patients and 29% in healthy volunteers.

When participants waited 60 minutes before drinking coffee, the researchers did not find the same reduction. Although the study was small, it helps explain why the timing of your morning coffee matters.

How long should you wait before drinking coffee?

The Teva levothyroxine package leaflet advises taking the tablet in the morning on an empty stomach with water. It specifically warns against taking it with coffee and recommends waiting between 30 minutes and an hour before having a cup.

SchildklierNL gives similar advice: take the tablet with water at least 30 minutes before breakfast, and leave at least an hour before drinking coffee.

The NHS also recommends waiting 30 to 60 minutes before having coffee or other caffeinated drinks.

A practical option is to take your tablet as soon as you wake up, then get dressed and ready for the day before making your first cup. Try to keep the interval consistent from one day to the next.

What if waiting an hour doesn't suit your routine?

If you find it difficult to wait before having breakfast or coffee, there may be another option worth discussing with your doctor: taking levothyroxine before going to bed.

The American Thyroid Association recommends taking the medicine either 60 minutes before breakfast or at bedtime, at least three hours after the evening meal. SchildklierNL also discusses evening dosing, with a recommended gap after eating or drinking.

However, don't switch your medication schedule yourself. Changing when you take levothyroxine can affect how much your body absorbs, so your thyroid levels may need to be checked afterwards. Speak to your doctor or pharmacist before making any changes.

Don't forget other medicines and supplements

Coffee isn't the only thing that can affect levothyroxine absorption. Calcium and iron supplements, certain antacids and some other medicines can also interfere with it.

The amount of time you need to leave between these products and your thyroid tablet depends on what you're taking. Some Dutch hospital guidance recommends a different interval from certain medicine leaflets, so there isn't one rule that applies to every product. Check your own package leaflet or ask your pharmacist.

If you've been taking your tablet alongside your usual morning coffee for a long time, don't suddenly change the routine without medical advice. The Teva leaflet specifically advises existing patients to have their thyroid levels checked by their doctor before changing their coffee habit.

A small change to your morning routine may help your medication work more consistently. The important thing is to make that change with the right medical guidance.

Medical disclaimer: This article is for general information only and should not replace personalised medical advice. Levothyroxine dosing and instructions can vary depending on your individual circumstances and the product you use. Always follow your prescription and package leaflet, and speak to your doctor or pharmacist before changing when or how you take your medication.