How Does Caffeine Affect Levothyroxine?

Levothyroxine is one of the most commonly prescribed thyroid medications and is used to replace or supplement natural thyroid hormone. Caffeine is a widely available substance found in coffee, tea, soft drinks, and chocolate.

Like many other drugs and medications, caffeine interferes with your body’s ability to absorb levothyroxine. You can still eat and drink foods containing caffeine if you follow your doctor’s instructions for levothyroxine dosing.

Levothyroxine

Levothyroxine, also called T4 or thyroid hormone, is sold under such brand names as Synthroid, Levoxyl, and Unithroid, according to the American Thyroid Association.

Doctors prescribe this medication to people with hypothyroidism, a condition in which the thyroid gland doesn’t produce enough thyroid hormone. It may also be prescribed to people with thyroid cancer, along with radioactive iodine therapy and surgery, according to StatPearls. The medication is usually taken every day in an oral tablet form and is generally required for life.

Many doctors recommend taking the medication on an empty stomach about 30 to 60 minutes before drinking caffeine-containing beverages or eating breakfast.

Caffeine

Caffeine is a bitter-tasting substance found in all non-decaffeinated coffees as well as many teas, sports drinks, and soft drinks. It’s also found in some pain-relief medications and even chocolate, although to a much lesser degree, according to Harvard Health Publishing.

Caffeine stimulates the nervous system and can help you stay alert, says Cleveland Clinic. The U.S. Food and Drug Administration (FDA) suggests drinking no more than 400 milligrams (mg) per day, which is about three cups of coffee. Having more than this, however, can cause you to feel anxious or jittery and have sleep issues or heart palpitations.

How Do Levothyroxine and Caffeine Interact?

A 2021 review of 63 studies reports that coffee can interfere with how your intestines absorb the medication and ultimately decrease its efficacy and safety.

However, this review is limited and has mixed results. More studies are needed to support these claims and understand how coffee and other beverages with caffeine may affect how your body absorbs levothyroxine.

Taking levothyroxine helps ease the symptoms of hypothyroidism. But if you’re not absorbing enough of the medication, you may begin to experience common symptoms of the condition, according to the Mayo Clinic. These symptoms can include:

• Fatigue or tiredness
• Constipation
• Muscle aches and weakness
• Joint pain
• Memory issues
• Depression

It’s important to talk with your doctor if you’ve been taking levothyroxine and have any symptoms after a change to how or when you take your medication. They may do a thyroid panel to determine your hormone levels, recommend lifestyle changes to avoid potential interactions, or change your current dose.

Recommendations for Use

If you take levothyroxine, you can still drink caffeine-containing beverages, but timing is important. You may be instructed to take levothyroxine on an empty stomach with a full glass of water and to avoid eating and drinking anything other than water for 30 minutes to an hour, according to StatPearls.

According to the 2021 review, drinking coffee one hour after taking the medication is generally safe and may prevent an interaction. This review also points out that other types of levothyroxine, such as softgel capsules or liquid forms, may not have the same effect, but more research is needed to support these claims. A 2022 study suggests that drinking coffee without milk or artificial sweeteners within five minutes of taking liquid levothyroxine doesn’t affect T4 levels.

However, another smaller 2022 study involving 37 participants in Taiwan found that drinking tea within one hour of taking levothyroxine may still interfere with the absorption of the medication.

Ultimately, it’s important to talk with your doctor to determine what’s right for you and your treatment plan.