Trust Thyroid Supplements?

I’ve gained weight, am tired all the time and have little energy. A friend suggested the problem could be my thyroid and suggested taking an over-the-counter thyroid supplement. Is this a good idea?

– August 26, 2016

The symptoms you describe could be caused by a thyroid problem, but they could also indicate a number of other health issues. I wouldn’t advise taking non-prescription thyroid supplements – often marketed to boost energy and metabolism as well as for “thyroid health”. Even if you know for sure that your thyroid is underactive, supplements containing herbs alone won’t help you since they can’t supply the hormones you need. More worrisome, however, are thyroid supplements that do contain thyroid hormones from animals or from synthetic sources. Too much or too little of these can affect your own hormone levels in a negative way.

Of particular concern, a study of over-the-counter thyroid supplements published in 2013 found that of 10 products claiming to boost thyroid function, nine contained thyroxine (T4) or triiodothyronine (T3) or both, and if you took some of them at the recommended doses you could get amounts as high or higher than those common in prescription medications. For example, if you took the recommended daily dose of one of the supplements tested, you would get 91 micrograms (mcg) of T4 and 16.5 mcg of T3. The starting dose for patients diagnosed with low thyroid function usually is 25 mcg of T4 per day. Excessive doses can cause insomnia, anxiety, and emotional changes, in addition to promoting bone loss and heart problems, the researchers warned.

About half the thyroid supplements tested in the study included iodine, which the body needs to make thyroid hormones. However, too much (or too little) iodine may be harmful. Labels on five of the products tested listed iodine as an ingredient, with amounts of 100 to 240 mcg in the recommended daily dose. The RDA for adults is 150 mcg.

Another problem: some thyroid supplements contain glandular extracts from cows. A Consumer Reports review of thyroid supplements published this year (2016) found that the ingredients listed on one of these products included raw thyroid, adrenal, pituitary and spleen bovine tissue. Ingesting these substances could pose a risk of Creuzfeldt-Jakob disease, a rare brain disorder (related to Mad Cow Disease) that is always fatal.

If you think you have a thyroid problem, see your physician. He or she can order simple blood tests that can tell you one way or the other. If you do have an underactive thyroid, you’ll need to take medication to get your hormone levels back in the normal range. The product most often prescribed is Synthroid, which contains only T4, one form of thyroid hormone. I prefer combination medications, such as Thyrolar, which provides both T3 and T4. Luckily, a thyroid deficit is very easy to correct. If that’s your problem, you’ll probably be amazed at how quickly your symptoms disappear once your hormone levels return to normal.

Remember, though, you’ll have to continue taking your thyroid pills and get periodic blood tests to make sure that the dosage is on target to keep those levels where they should be.

Andrew Weil, M.D.

Victor J. Bernet et al, “Thyroxine and Triiodothyronine Content in Commercially Available Thyroid Health Supplements.” Thyroid, September 25, 2013, doi:10.1089/thy.2013.0101.

Related Weil Products

Weil Vitamin Advisor for Supplements and Herbs

If you are interested in supplementing your diet, and want to take the mystery out of choosing vitamins, try the Weil Vitamin Advisor. Visit today for your free, personalized recommendation.
Get Started

Share Dr. Weil's expertise with your friends & family