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Can Grapefruit Juice Be Drunk if You Are Taking Thyroid Medicine?

By Frankie Smith ; Updated July 18, 2017

Grapefruits are a nutritional powerhouse, loaded with vitamins and minerals, such as vitamins C and A, potassium, calcium and magnesium. A popular breakfast food, grapefruit has received attention not only for its health benefits but also its tendency to interact with some medications. Discuss possible drug interactions with your doctor, as grapefruit juice may affect absorption of thyroid medications.


Your thyroid is a small, 2-inch, gland located at the front of your neck. Just below your voice box, this small gland plays a large roll in metabolism. According to the University of Maryland Medical Center, the thyroid secretes two iodine-rich hormones called thyroxine, or T4, and triiodothyronine, or T3. These two hormones play a central role in metabolism, stimulating every cell in your body. The more active the cells are, the harder your organs work in response.

Thyroid Disorders

Thyroid disorders occur when your body produces too little or too much of the T3 and T4 hormones. Hypothyroidism is a disorder marked by an under active thyroid gland. According to, women, particularly those older than 50 years old, more frequently experience this disorder presenting symptoms such as fatigue, achy joints, unexplained weight gain and puffy face. Hyperthyroid occurs when the thyroid secretes too much hormones, resulting in symptoms, such as sudden weight loss, increased appetite, anxiety, rapid heart beat and difficulties with sleep.


Treatment of thyroid disorders differ dependent on whether you are producing too much, or too little of the thyroid hormones. Hypothyroid is most frequently treated with a synthetic thyroid hormone called levothyroxine, reports This medication helps to restore proper hormone balance once proper dosing is determined. Hyperthyroidism may be treated in a few ways, including radioactive iodine, anti-thyroid medications, beta blockers or surgery.

Grapefruit Interactions

Grapefruits contain several components called furanocoumarins, which inhibit certain isoenzymes in the intestinal wall. This delayed function of the intestines prompts production of more enzymes. According to "Food-Medication Interactions: 14th Edition," consuming grapefruit increases the amount of metabolized drug that enters the system for up to 72 hours after ingesting the grapefruit. This increase in drugs entering the system may lead to higher amounts of therapeutic effect, higher rates of side effects and greater toxicity.


A study published in the September 2005 edition of the "British Journal of Clinical Pharmacology" reports drinking grapefruit juice slightly delays absorption of levothyroxine, finding it had a small effect on bio-availability of the medication. This research is supported by an article published in the November 2010 edition of the "British Journal of Clinical Pharmacology," which reports a drop in the bio-availability of the hormone thyroxine even when patients were administered a higher dose of the medication.

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