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Taking Thyroid Medicine Properly

Taking thyroid medicine with vitamin C but without coffee, fiber, food or minerals results in the best absorption and maximum effectiveness.

Millions of people suffer from an underactive thyroid gland. That is why the synthetic thyroid hormone levothyroxine (Synthroid, Levothroid, Levoxyl, Unithroid, etc.) is one of the most widely prescribed medications in the pharmacy. This can be a relatively simple fix for a difficult problem, but only if you are taking thyroid medicine properly. Many readers would like to know about how to do that.

Be Alert for Interactions with Minerals:

Q. My thyroid gland doesn’t work very well, so I have been taking levothyroxine. My new doctor has suggested a multivitamin and a calcium supplement. Can I take all these pills at once? I know some things don’t agree with the thyroid hormone.

A. You’ve been paying attention. Calcium can interfere with the absorption of levothyroxine (Pharmaceuticals, March 2, 2021).  If your multivitamin contains iron, that might also pose a problem.

It isn’t hard to get around this difficulty, though. Simply take your nutritional supplements at a different time. When you check the label on your multivitamin, also look to see if it contains biotin. That B vitamin can interfere with accurate thyroid test results, so you may want to discontinue the multi for a couple of days before your regular blood work.

Avoiding Interactions with Levothyroxine:

Q. I’ve been taking levothyroxine for more than a dozen years. I just recently learned I’ve been taking it at the wrong time. I was taking it along with breakfast and coffee, not to mention vitamins, minerals, probiotics, Citrucel and other medications. I am totally confused about how to take it properly.

A. Taking your thyroid medicine with coffee, mineral supplements (especially iron or calcium) or fiber such as bran cereal or Citrucel can interfere with its absorption (Thyroid, March 2008).  Using a calcium-fortified fruit juice to take the medication could severely limit how much gets into your bloodstream. So could a high-calcium food like Greek yogurt. Other foods that may cut absorption of levothyroxine include grapes, soybeans and papaya (European Review for Medical and Pharmacological Sciences, 2014).

Watch Out for Drugs:

Drug interactions can be troublesome. There are several medications, especially those intended to moderate stomach acid, that can also interfere with proper absorption (Journal of Pharmacy & Pharmaceutical Sciences, 2015). Proton pump inhibitors (esomeprazole, omeprazole, etc.) at high doses may affect absorption. So do antacids taken at the same time as the thyroid pill.

One supplement that you might want to include with your thyroid is vitamin C. In one randomized controlled study, swallowing the pill with water containing 500 mg ascorbic acid dissolved in it improved absorption as determined by lower TSH and higher levels of T4 and T3 (Journal of Clinical Endocrinology and Metabolism, June, 2014).

Taking Thyroid Medicine at Bedtime:

Why not take your levothyroxine at bedtime? A small study showed that the drug is absorbed better in the evening (Clinical Endocrinology, Jan., 2007). As long as you don’t eat within two or three hours of retiring, your thyroid medication should work fine and nothing else will interfere with it.

An alternative to that would be Tirosint. This liquid formulation is designed to be absorbed much better, without interference from breakfast beverages such as coffee or a latte (Pharmaceutics, Dec., 2013).

Learn More:

You can learn more about maximizing the effectiveness of levothyroxine in our Guide to Thyroid Hormones. For more discussion of the nuances of treatment of hypothyroidism, you may wish to listen to our interview with Dr. Antonio Bianco. It is Show 1330: Rethinking Hypothyroidism.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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  • Wiesner A et al, "Levothyroxine interactions with food and dietary supplements-A systematic review." Pharmaceuticals, March 2, 2021. DOI: 10.3390/ph14030206
  • Benvenga S et al, "Altered intestinal absorption of L-thyroxine caused by coffee." Thyroid, March 2008. DOI: 10.1089/thy.2007.0222
  • Ianiro G et al, "Levothyroxine absorption in health and disease, and new therapeutic perspectives." European Review for Medical and Pharmacological Sciences, 2014.
  • Seng Yue C et al, "When bioequivalence in healthy volunteers may not translate to bioequivalence in patients: Differential effects of increased gastric pH on the pharmacokinetics of levothyroxine capsules and tablets." Journal of Pharmacy & Pharmaceutical Sciences, 2015. DOI: 10.18433/j36p5m
  • Jubiz W & Ramirez M, "Effect of vitamin C on the absorption of levothyroxine in patients with hypothyroidism and gastritis." Journal of Clinical Endocrinology and Metabolism, June, 2014. DOI: 10.1210/jc.2013-4360
  • Bernareggi A et al, "Oral liquid formulation of levothyroxine is stable in breakfast beverages and may improve thyroid patient compliance." Pharmaceutics, Dec., 2013. DOI: 10.3390/pharmaceutics5040621
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