Key takeaways

Switching between brands or generics of levothyroxine can affect the medication’s absorption and effectiveness, so consistency is key.
Certain foods, including soy-based foods, cottonseed meal, grapefruit, walnuts, high-calcium foods, and high-fiber foods, can decrease the absorption of thyroid medication when taken too close to the dose.
Drinking coffee too soon after taking thyroid medication can reduce the amount of medication the body absorbs. For morning coffee drinkers, taking levothyroxine at night might be a solution, but it still must be taken on an empty stomach, with a full glass of water.
Vitamins and supplements containing iron, calcium, or magnesium should be avoided for at least four hours after taking thyroid medications to prevent interaction, and certain medications should never be taken with thyroid medication due to potential adverse interactions.

Have you been feeling tired and achy, or gaining weight and you just can’t figure out why? It could be an underactive thyroid. Your thyroid, a butterfly-shaped gland in your neck, controls the growth and metabolism of virtually every part of your body. When it’s out of balance, even simple, everyday routines may seem like a monumental task.

If you’re newly diagnosed with underactive, or hypothyroid, you may have to take medicine for the rest of your life. That means an adjustment to your daily routine and your lifestyle. Thanks to thyroid medication interactions, your treatment plan can interfere with your daily coffee, a cheese plate after work, or vitamins and supplements you take. Your specific needs will be something you’ll want to discuss with your doctor to help you to start feeling better and getting on with life.

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What medications treat hypothyroidism?

Levothyroxine is the most common prescription used to treat hypothyroidism. This medication is also known by several brand names, including:

Whether your healthcare provider prescribes the generic or brand name, these medications help to replace the thyroid hormone your body isn’t naturally producing in your blood.

It may take some time to find the right medication, or dosage that works for you—and once you’ve figured out your treatment plan, certain things can mess with how the prescription works for you.

5 things you should avoid when taking thyroid medication

If you’re new to taking daily prescription medication, you may be surprised that certain thyroid medications interact with common drugs, supplements, and even foods. Here, primary care providers weigh in on the thyroid medication interactions you should know about.

1. Changing brand names

Since most of the medications for hypothyroidism contain the same active ingredient (levothyroxine), it might seem harmless to switch between brand names. But, there’s reason to believe that switching between brands or generics could impact how your body reacts to or absorbs the synthetic hormone. The American Thyroid Association recommends consistency in treatment. In other words, continue taking the same generic (i.e., from the same pharmacy) or the same brand name, unless you check with your doctor first.

2. Certain foods

“Levothyroxine is ideally taken on an empty stomach, at least 30 minutes before meals,” according to Rajnish Jaiswal, MD, associate chief of emergency medicine at Metropolitan Hospital Center in New York City. “Taking it with meals has shown to decrease its absorption from the gut.”

Eating certain foods too close to your daily dosage can interfere with how the medication works, including:

Soy-based foods or flours, like edamame, tofu, or miso
Cottonseed meal
Grapefruit or grapefruit juice
Walnuts
High-calcium foods, like milk, yogurt, or cheese
High-fiber foods, like broccoli, cabbage, or kale

Fatty, fried, or sugary foods can also slow your metabolism and make it harder to absorb medication. If you have trouble remembering to take the medication before eating, discuss your options with your doctor to find a routine that works.

3. Your daily coffee

We all love our cup of morning joe. Can you still drink coffee after taking thyroid medication? Yes, but your timing is crucial if you want the medicine to work properly.

“Do not drink coffee, not even a sip unless it has been at least an hour since you took your levothyroxine. Coffee will also reduce the amount of medication your body absorbs,” says Tricia Eichenlaub, MSN, APRN, FNP-C, of King’s Daughters Internal Medicine Clinic in Portsmouth, Ohio.

Mornings are hectic enough without remembering to wait 60 minutes between taking your thyroid and grabbing a Starbucks latte. Fortunately, levothyroxine and coffee doesn’t have to be a problem, says Eichenlaub, who goes on to say, “Levothyroxine can be taken on an empty stomach by itself with a full glass of water at night. Just remember to take it at the same time each night.” This can also work for people who have trouble avoiding certain foods.

4. Vitamins and supplements

“You should also avoid any drugs or supplements that contain iron, calcium, or magnesium for at least four hours after taking your thyroid medications,” says Dr. Jaiswal. That also includes multivitamins that contain these minerals.

When having your thyroid levels tested, you should avoid biotin, as it can interfere with accurate measurement. Usually, it is recommended to stop biotin for 1-2 weeks prior to checking thyroid labs. Too much iodine can also cause levothyroxine interactions.

It’s always good to check with your endocrinologist or primary care physician beforehand if you regularly use or plan to add supplements or any other medications to your regimen.

5. Other medications

Because regulating hormone levels in the body is so important, some common drugs can’t be taken with thyroid medication. Which ones should you never take along with thyroid medication?

According to Dr. Jaiswal, some of the common prescription and over-the-counter medications that interact with levothyroxine are:

Antibiotics: ciprofloxacin, rifampin
Seizure medications: phenytoin, fosphenytoin, and carbamazepine
Antidepressants: amitriptyline, fluoxetine
Antacids and indigestion remedies: Omeprazole, pantoprazole, ranitidine, Tums and Pepto-Bismol
Ulcer medications: Carafate (sucralfate)
Cholesterol-reducing drugs: Prevalite (cholestyramine) and Colestid (colestipol)

It’s all about getting the right thyroid medication at the proper dosage—and avoiding these things that throw that off—to help regulate your levels and let you feel better and get on with life.