How Coffee Interferes With Synthroid (Levothyroxine)

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Many people like to drink a cup of coffee before heading to work or getting the day started. But if you are taking the thyroid drug levothyroxine, drinking coffee one hour before or after a dose can make it less effective.

Levothyroxine (marketed under the brand names Synthroid, Levoxyl, Unithyroid, and others) is affected by caffeine in coffee and other caffeinated beverages. It affects the absorption of the drug in the intestines and lowers the amount that enters the bloodstream. Without enough of the hormonal drug in your body, you can develop symptoms of hypothyroidism (low thyroid function).

Caffeine affects both levothyroxine pills and tablets but not liquid or gel formulations.

This article looks at how caffeine affects levothyroxine in its different forms and whether switching to a different thyroid drug is an option.

Effects of drinking coffee in close succession to thyroid medication.

Verywell / Melissa Ling

Caffeine and Levothyroxine

When you're taking levothyroxine, caffeine can decrease the levels of the synthetic version of the thyroid hormone T4.

Levothyroxine is used in people with hypothyroidism whose thyroid glands are not producing enough of a hormone called T4 to keep the body functioning normally. Levothyroxine is a synthetic compound identical to T4 that is used when the thyroid gland isn't working correctly or has been removed.

Doctors generally recommend that you take your thyroid drugs in the morning on an empty stomach and that you wait an hour before eating. Eating before levothyroxine has time to be fully absorbed can lower the amount of the drug that enters the bloodstream.

How Caffeine Affects Absorption

Coffee and other caffeinated beverages affect the absorption of the drug in different ways. Studies have found that drinking coffee with levothyroxine decreases absorption by increasing the speed at which the drug passes through the intestines.

Caffeine is a stimulant that can increase gut motility, meaning the muscle contractions that move food through the digestive tract. Caffeine also has a mild laxative effect and increases the amount of fluid in stools.

Both of these things can cause levothyroxine to move through the intestines too quickly before it has the chance to be absorbed. When this happens, your thyroid hormone levels can drop and lead to symptoms of hypothyroidism, including fatigue, muscle weakness, weight gain, hoarseness, and sensitivity to cold.

Levothyroxine absorption may also be decreased when taken with black tea, hot cocoa, or caffeinated soft drinks.

What About Other Thyroid Medications?

Other types of thyroid drugs, including liothyronine and antithyroid drugs, are not affected by caffeine.

Liothyronine (marketed under the brand name Cytomel) is more readily absorbed in the digestive tract and doesn't rely so much on stomach acids to be broken down as levothyroxine does. Even so, liothyronine should still be taken on an empty stomach.

Antithyroid drugs like Tapazole (methimazole) used to treat hyperthyroidism (overactive thyroid) are easily absorbed and can be taken with or without food.

Levothyroxine Forms Not Affected By Caffeine

Certain non-tablet formulations of levothyroxine are designed to be absorbed quickly in the digestive tract and are not affected by caffeine in the same way as tablets or pills.

Tirosint is a soft gel form of levothyroxine, and Tirosint-Sol is the liquid form. These medications are absorbed more rapidly than the standard formulations. The gel and liquid forms were developed for people who have digestive disorders such as celiac disease that prevent the proper absorption of nutrients.

Studies have also shown that Tirosint or Tirosint-Sol can be taken at the same time as coffee without any problems with absorption or any effects on T4 levels.

Strategies for Coffee Drinkers

Not everyone will want to wait an hour to have coffee in the morning. For these people, it is perfectly reasonable to take your levothyroxine dose at night just before bedtime. For some, it is easier to do so because they will have eaten hours beforehand and simply need to avoid snacking three to four hours before bedtime.

A 2022 study in Frontiers in Medicine concluded that there was no difference in the effectiveness of levothyroxine (as measured by drug concentrations in the blood) in people who took their dose in the morning or at bedtime.

Another possible solution is to drink decaffeinated coffee. Compared to caffeinated coffee, decaffeinated coffee doesn't speed up gut motility as much. When it does, the contractions tend to occur at the proximal (distant) end of the colon near the rectum rather than in the upper part of the small intestine where most of the levothyroxine is absorbed.

Switching Medications

Switching from your current levothyroxine formulation to another is not generally recommended because it can cause your thyroid levels to fluctuate.

However, if you are having problems with absorption due to conditions like chronic diarrhea or celiac disease and are experiencing fluctuations in your T4 levels, switching to another form may be a solution. Speak with your healthcare provider to see if Tirosint or Tirosint-Sol may be a reasonable option.

Even if caffeine doesn't affect their absorption, both Tirosint and Tirosint-Sol still need to be taken on an empty stomach.

If you do switch, be sure to take your medications as prescribed and follow up with routine blood tests to ensure that the dose is correct and your T4 levels are normal.

Should You Switch Medications?

While switching from levothyroxine to Tirosint or Tirosint-Sol may seem like an easy fix to your morning coffee dilemma, experts generally advise against it.

A 2020 analysis in Advances in Therapy evaluated the medical records of 19,850 people treated with levothyroxine over a period of six years, half of whom switched to other formulations (including bioidentical generic pills or tablets) and half of whom stayed with the same treatment for the study period.

According to the researchers, those who switched were more likely to have abnormal T4 levels and more likely to have complications associated with poorly controlled hypothyroidism. The study suggested that people who switch tend not to remain in consistent care and will typically address health concerns by requesting a change in treatment.

So unless your T4 levels are abnormal despite taking your medications as you should, it may be best to avoid switching for the sake of coffee.


Caffeine in coffee and other caffeinated beverages can affect the absorption of the thyroid drug levothyroxine by making the drug pass through your gut too quickly. This can cause your T4 hormone levels to drop or fluctuate.

To avoid this, levothyroxine should be taken on an empty stomach, and you should wait an hour before eating anything or drinking a caffeinated beverage.

If you have trouble controlling your thyroid hormones and your doctor believes that intestinal absorption is to blame, you may be switched to the soft gel or liquid formation of levothyroxine called Tirosint and Tirosint-Sol.

Frequently Asked Questions

  • What foods and supplements can interfere with thyroid medication?

    Besides coffee, some other foods, supplements, and medications can affect how well levothyroxine works. These include:

    • Foods containing soy and cottonseed meal
    • Walnuts
    • Dietary fiber
    • Grapefruit juice
    • Iron supplements
    • Calcium supplements
    • Antacids
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."