Do's and Don'ts of Taking Thyroid Meds

If you have hypothyroidism and take thyroid hormone — Synthroid, Levoxyl or Tirosint brands of levothyroxine — you may wonder if there are foods that might interfere with its absorption or boost its potency. As it turns out, there are no dietary restrictions, but when you eat is key.

The thyroid is a butterfly-shaped gland located in the middle of your lower neck. As the Cleveland Clinic explains, it produces hormones responsible for controlling your body's metabolism — how quickly your cells carry out tasks in order for you to function.

If your thyroid isn't producing enough thyroid hormone to keep your body running, you have an underactive thyroid, a condition called hypothyroidism.

The most common reason for hypothyroidism is an autoimmune disease, which happens when your immune system (responsible for protecting your body from infectious "invasions"), mistakes thyroid gland cells for "invaders" and attacks them, according to the American Thyroid Association. Then, there aren't as many thyroid cells to produce the right amount of thyroid hormone.

Levothyroxine is a synthetic thyroid hormone, taken orally, that is used to treat hypothyroidism. There are several brand names, including Synthroid, Levoxyl, Tirosint and Levo-T, according to the Mayo Clinic.

​Read more:​ How to Manage Hypothyroidism With Diet and Exercise

Synthetic thyroid hormone can restore adequate hormone levels and reverse the signs and symptoms of hypothyroidism. However, there are a few tricks to taking it correctly.

​When to eat.​ Any brand of levothyroxine should be taken on an empty stomach, and with at least half to one full glass of water, advises Stephanie Lee, MD, PhD, director of the Thyroid Health Center at Boston Medical Center.

She recommends waiting for about 30 minutes before eating, as a general rule. "However, if you have other medical problems that can cause a change in the rate of stomach emptying, such as diabetes or gastric bypass, you should wait longer — perhaps up to an hour before eating," says Dr. Lee, who is also a professor of medicine at Boston University School of Medicine.

She often recommends that levothyroxine be taken at bedtime because absorption is better during the night than in the morning. "In that case, I tell patients to wait two or three hours after eating before taking the medication," Dr. Lee says.

​Foods to watch.​ Dr. Lee recommends that thyroid hormone pills be taken with water, rather than with milk or coffee, as they can interfere with levothyroxine absorption. "Some people take levothyroxine in the morning, and coffee with milk is a common breakfast food, so it's important to be aware of this," she says.

According to the Mayo Clinic, foods with too much dietary fiber also can interfere with the absorption of levothyroxine and should not be taken at the same time. So can walnuts, soy products and cottonseed meal. But you can safely enjoy them at other times of the day.

​When to take other meds.​ "Some people take all their medications at the same time, but there are medications that can interfere with the absorption of levothyroxine and should be taken at a different time of day," says Dr. Lee. These include iron and iron-containing supplements (such as multivitamins), calcium and supplements containing fat, such as vitamin E or fish oil.

Antacids, which usually contain aluminum, calcium or magnesium, similarly shouldn't be taken together with levothyroxine, Dr. Lee says. And antacids such as sucralfate (Carafate), which coat the stomach lining, also can block levothyroxine from being absorbed.

Preparations that reduce stomach acid, such as omeprazole (Prilosec) and famotidine (Pepcid), have been shown to have a variable effect on levothyroxine absorption in research studies. Generally, it is recommended to not take these medications at the same time as levothyroxine, she adds.

Certain cholesterol-lowering medications, such as those containing cholestyramine (Prevalite) and colestipol (Colestid) can likewise interfere with levothyroxine absorption. On the other hand, estrogen-containing products (such as birth control pills or hormone replacement therapy) can increase the binding and sequestration of levothyroxine, which may mean your dosing amount will need to be increased to keep the thyroid levels normal, Dr. Lee explains.

All of these products should be taken three to four hours before or after you take your thyroid medication, Dr. Lee advises.

​Read more:​ Levothyroxine and Vitamin Supplements