What high fiber foods should I avoid when I take levothyroxine?

Diets that contain high fibre can interfere with absorption of levothyroxine. Levothyroxine replaces thyroid hormone and is prescribed to patients with hypothyroidism. Since fibre affects the rate of food absorption in the body, it can affect the amount of medication the body absorbs.


Cabbage, like other high-fibre foods, interferes specifically with iodine uptake. Preventing iodine from being absorbed inhibits the body from producing thyroid hormones.


Walnuts can also interfere with the absorption rate of levothyroxine. Walnuts are a high source of fibre and omega 3, which helps prevent cardiovascular diseases. The daily limit of walnut consumption when taking levothyroxine is 12 grams. Any amount beyond that will interfere with the medication.

St. John’s Wort

St. John’s Wort has traditionally been used for pain relief, anti-diarrhoea, and anti-inflammatory treatment. It also has many drug contraindications including levothyroxine. It interferes with absorption time and decreased the activity of levothyroxine in the body.

Other foods

Other sources of fibre include apples, raspberries, pears, black beans, peas, lentils, artichokes, broccoli, brussels sprouts and soybeans.


Changing the amount of fibre in a daily diet can affect the amount of levothyroxine the body absorbs therefore decreasing the effectiveness of the drug. This is due to the fact that fibre speeds up the absorption process of food in the body. If diet habits fluctuate, check thyroid hormones levels every six to eight weeks to assure normal hormone levels in the body. Maximum absorption of levothyroxine is best when taken early in the morning on an empty stomach one hour before consuming food.

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About the Author

Sonya Kanti has more than five years of experience writing professionally. Currently in medical school, she focuses her writing on health-related issues. She's written for the "PITT MED" medical magazine published by the University of Pittsburgh Medical School. She has a Bachelor of Arts degree in political science with a minor in biochemistry from Loyola University Chicago.