6 Thyroid Medication Mistakes You Don't Want to Make

Plus, how to get the absolute most out of your thyroid meds

Written by Sari Harrar

For about one in seven of the 10-12 million Americans with an underactive thyroid gland, conventional treatment with the synthetic thyroid hormone levothyroxine just isn’t enough.1  Sometimes, the cause is simple and easy to fix —you may need a dose adjustment, a change in when you take your thyroid medication or in where you store it, for example.  For others, the reasons are more mysterious and controversial. For instance,  some experts say some people with hypothyroidism may benefit from adding a second thyroid hormone called T3.  If you continue to feel sick, tired, depressed or have symptoms like stubborn weight gain, don’t reach for an over-the-counter thyroid booster (there can be dangers; see #5). It’s worth talking with your doctor about the best solution for you. Here are five thyroid medication mistakes that you might be making:

#1. You expect to feel better instantly. Some people start feeling more energetic and alert within a week or two of starting thyroid hormone. But for others, it could take a month or two to feel better. And you may have to see your doctor several times for tests of your blood levels of thyroid stimulating hormone (TSH) and adjustments to your levothyroxine dose to get it just right. 2

 #2. You take your meds at the wrong time. For best absorption into your bloodstream, levothyroxine should be taken on an empty stomach  30-60 minutes before breakfast, or three or more hours after dinner. Taking it with or too soon before or after a meal or snack could reduce absorption to 64%, from a high of 80% when you’re fasting, according to the American Thyroid Association (ATA).3 Just changing your timing could bring your thyroid levels back into a normal range.

In one older but often-cited Italian study4 of four people whose thyroid numbers were not in control despite taking thyroid hormone, researchers found that they all took their medication just 15-20 minutes before breakfast. Changing their routine, so they took thyroid hormone 60 minutes before their morning meal, improved their numbers within a month. Take it with water. In another Italian study, coffee interfered with absorption.5 And don’t take antacids or supplements containing calcium or iron with four hours of your levothyroxine.6 Iron can make levothyroxine less effective according to the National Institutes of Health Office of Dietary Supplements 7. Calcium can interfere with absorption.8

#3. You switched from a brand-name to generic levothyroxine. Switching from a brand-name to generic thyroid hormone, or vice-versa could affect your TSH levels – even if the dose is the same. 9 The US Food and Drug Administration requires that all levothyroxine preparations deliver 95-105% of the potency on the label. But, the ATA notes, even tiny variations could make a difference. That’s why the group’s guidelines recommend sticking with the drug type (generic or brand name) to keep your TSH levels steady. (Ask for it at every refill.) If you’ve made a switch and have concerns, have your doctor retest your TSH level, the ATA, the American Association of Clinical Endocrinologists, and The Endocrine Society have recommended in a joint statement. 10

#4. You store your levothyroxine tablets in the wrong place. Keep this drug in cool, dry, dark place, like in a cabinet or on a shelf in a closet away from high-humidity environments like your bathroom.  Exposing pills to excess heat, light, and moisture can make thyroid medications less effective. In a recent Italian study, one in 20 people with hypothyroidism whose TSH levels stayed outside the normal range despite taking levothyroxine had been stashing their tablets in the wrong places—next to heaters, near the shower in the bathroom, or in clear containers on tables beside a window. When they started keeping them in a better spot—and took those pills— their symptoms were reduced. 11

#5. You think adding T3 will help. Stories about the purported wonders of “T3” for hypothyroid symptoms are all over the internet. Some endocrinologists recommend that people whose hypothyroidism symptoms persist despite normal TSH levels try adding synthetic triiodothyronine (T3) to their levothyroxine therapy. It could work, but research suggests it doesn’t help everyone.

 T3 is the body’s active form of the thyroid hormone thyroxine. Enzymes in organs like the liver, brain, and heart convert thyroxine (T4) into T3 and the thyroid gland produces some as well. For most people with hypothyroidism, the body converts levothyroxine into sufficient T3. But there’s evidence this doesn’t always happen. For about 15% of people with treated hypothyroidism whose TSH levels are in the normal range, T3 is still low, experts note.12 Taking a combination of T3 plus T4 can raise T3 levels… but that doesn’t always relieve lingering hypothyroidism symptoms, according to a recent review of 11 combo-therapy studies involving 1,216 people with hypothyroidism. Problems like tiredness, body aches, depression and weight gain did not improve significantly. 13 A 2016 Brazilian study of 32 people with hypothyroidism found that adding T3 didn’t improve their clinical symptoms any more than taking T4 alone. 14  And yet, combining T3 and T4 does seem to help some people – even when it doesn’t seem to raise their T3 levels.  In one new study, published in April 2017 in the European Thyroid Journal, researchers found that combination therapy helped 24 out of 37 people in this situation – but it didn’t seem to matter whether they had low T3 levels beforehand or if their levels rose during treatment. 15

What’s going on? One clue is emerging. Early research from Chicago’s Rush University suggests that a genetic mutation could be responsible for lingering symptoms despite healthy TSH levels —by preventing enzymes from converting T4 into T3 in the body.  But more studies are needed. 16

What should you do? If you’re curious about T3, talk it over with your doctor. It’s also wise to check that your health insurance covers testing and treatment.  The ATA’s 2012 guidelines say L3-L4 combo therapy shouldn’t be used routinely because long-term studies have yet to prove it has benefits. But major groups outside the U.S., like the European Thyroid Association (ETA), say doctors there should consider it an “experimental treatment modality” for people whose fatigue, depression, weight gain and other hypothyroidism symptoms haven’t waned even though taking levothyroxine alone has moved their TSH levels into the normal range. 17

 #6. You take "natural" thyroid medications and supplements. Many supplements claim to “support” thyroid health – but some are laced with thyroid hormones not listed on the label. Adding them to your medication could mean making a thyroid medication mistake of getting too much. In a 2013 study of 10 top-selling thyroid-support products sold on the internet, researchers from Germany’s Landstuhl Regional Medical Center and from the Walter Reed Army National Military Medical Center in Bethesda, MD, found that nine were laced with T3, T4 or both in a variety of amounts. Ingredient labels listed animal thyroid tissue for some while others only listed herbs such as ashwagandha, guggul, and Coleus forskohlii. The researchers concluded that drugs were added to the supplements.18 Supplements, including types containing a seaweed called kelp, may also contain dangerously high levels of iodine. Some experts also warn about an extremely rare threat that doesn’t seem to have ever actually happened, but could. Natural thyroid supplements may contain gland tissue from the thyroid, liver, heart, pancreas and other animal organs of cows—raising a tiny but serious risk for exposure to prions— agents that could transmit the brain disease Creutzfeldt–Jakob.19


1. “Guidelines for the Treatment of Hypothyroidism.” Jonklas J et al. THYROID.

Volume 24, Number 12, 2014. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267409/

2. https://www.endocrineweb.com/conditions/thyroid/hypothyroidism-too-little-thyroid-hormone-0

3.  “Guidelines for the Treatment of Hypothyroidism.” Jonklas J et al. THYROID.

Volume 24, Number 12, 2014. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267409/

4. “Delayed intestinal absorption of levothyroxine.” Benvega S et al. Thyroid. 1995 Aug;5(4):249-53. https://www.ncbi.nlm.nih.gov/pubmed/7488863

5. “Altered intestinal absorption of L-thyroxine caused by coffee.” Benvenga S et al. Thyroid 2008; 18:293-301. https://www.ncbi.nlm.nih.gov/pubmed/18341376

6. “Levothyroxine.” National Library of Medicine. URL: https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0001057/ https://medlineplus.gov/druginfo/meds/a682461.html#special-dietary

7. “Iron.” National Institutes of Health Office of Dietary Supplements. URL: https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/

8. “Interaction between levothyroxine and calcium carbonate.” Masokopakis EE et al. Can Fam Physician. 2008 Jan; 54(1): 39 . URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2293315/

9. “Guidelines for the Treatment of Hypothyroidism.” Jonklas J et al. THYROID.

Volume 24, Number 12, 2014. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267409/

10. AACE, TES, and ATA: Joint Position Statement on the Use and Interchangeability of

Thyroxine Products. American Association of Clinical Endocrinologists, The Endorine Society and the American Thyroid Association.

11.  “Refractory Hypothyroidism Due to Improper Storage of Levothyroxine Tablets.”  Benvenga S et al. Front Endocrinol (Lausanne). 2017 Jul 10;8:155. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5502408/

12. “Thyroid Hormone Replacement Therapy: Three ‘Simple’ Questions, Complex Answers.” Bianco A et al. Eur Thyroid J 2012;1:88–98. URL: https://www.ncbi.nlm.nih.gov/pubmed/24783002

13. “Thyroxine-triiodothyronine combination therapy versus thyroxine monotherapy for clinical hypothyroidism:

meta-analysis of randomized controlled trials.” Grozinsky-Glasberg S et al. J Clin Endocrinol Metab 2006; 91: 2592–2599. URL: https://www.ncbi.nlm.nih.gov/pubmed/16670166

14. “Treatment of hypothyroidism with levothyroxine plus liothyronine: a randomized, double-blind, crossover study.  Kaminski J et al. Arch Endocrinol Metab. 2016 Nov-Dec;60(6):562-57. URL: https://www.ncbi.nlm.nih.gov/pubmed/27982198

15. “Neither Baseline nor Changes in Serum Triiodothyronine during Levothyroxine/Liothyronine Combination Therapy Predict a Positive Response to This Treatment Modality in Hypothyroid Patients with Persistent Symptoms.” Medici BB et al. Eur Thyroid J. 2017 Apr;6(2):89-93. URL: https://www.karger.com/Article/FullText/454878

16. “Prevalent polymorphism in thyroid hormone-activating enzyme leaves a genetic fingerprint that underlies associated clinical syndromes.” EA McAnnich et al. J Clin Endocrinol Metab. 2015 Mar;100(3):920-33

17. “2012 ETA Guidelines: The Use of L-T4 + L-T3 in the Treatment of Hypothyroidism.” European Thyroid Association. Eur Thyroid J. 2012 Jul; 1(2): 55–71.URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821467/?report=classic

18. “Thyroxine and Triiodothyronine Content in Commercially Available Thyroid Health Supplements.” Kang GK et al.   Thyroid. September 2013, 23(10): 1233-1237. URL: http://online.liebertpub.com/doi/abs/10.1089/thy.2013.0101?journalCode=thy&

19.  “5 Reasons You Should Never Take Thyroid Supplements.” Consumer Reports, March 26, 2016. URL: https://www.consumerreports.org/vitamins-supplements/never-take-thyroid-supplements/

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