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What Supplements Should I Avoid While Taking Thyroid Hormones?

Question:
I take levothyroxine (Synthroid), a thyroid hormone to treat hypothyroidism. Are there supplements I should avoid, or be taking, due to this drug?

Answer:
Levothyroxine (Synthroid, Levoxyl), liothyronine (Cytomel), and other thyroid hormone drugs for hypothyroidism (underactive thyroid), can be affected by taking supplements and can affect your ability to absorb certain vitamins and minerals. These interactions are explained in the Hypothyroidism article in the Conditions section of our website, and Thyroid Hormone article, which is part of the extensive Drug Interactions section (where you can look up interaction for other drugs you may be taking). Care must be taken with regard to using these supplements, which include calcium, iron, and soy (including soy protein powders and soy isoflavones -- found in some menopause supplements) (which can affect absorption of thyroid hormone drugs), alpha-lipoic acid (which may lower levels of thyroid hormone T3 and increase levels of TSH) and L-carnitine and acetyl-l-carnitine (which can inhibit the activity of thyroid hormones -- and may help people with hyperthyroidism, or overactive thyroid).

Antacids containing aluminum hyrdroxide and magnesium hyroxide  (such as Maalox) should be taken at least four hours before or after taking levothyroxine, as they may delay or prevent the absorption of the drug (Synthroid Prescribing Information 2017).

There is some evidence that kelp supplements (such as tablets and capsules) can increase levels of TSH (thyroid-stimulating hormone).

Although often promoted for thyroid health, iodine supplements will not help your thyroid work better, and may even cause problems, unless you have an iodine deficiency.
 
Preliminary evidence suggests ashwagandha may increase thyroid hormone levels, and so should be used with caution in people taking thyroid hormones, or people with hyperthyroidism.

Be aware that high doses of biotin (as found in some B-complexes or supplements for hair and nails) may interfere with certain thyroid laboratory tests.

Resveratrol has been shown to increase TSH levels and cause thyroid enlargement in animals, although it's not known whether it effects thyroid function in people. 

Long term exposure to high or even moderate amounts of lithium can affect thyroid function.

Also, be aware that some thyroid-boosting supplements, including herbal supplements, have been found to contain thyroid hormones at significant levels, which are not listed and may be due to drug spiking. See the details in our Warnings section.

Certain foods and drinks may also interfere with absorption or bioavailability of levothyroxine. Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine from the gastrointestinal tract; grapefruit juice may delay the absorption and reduce its bioavailability (Synthroid Prescribing Information 2017). There is also some evidence that drinking coffee at the same time as taking levothyroxine can reduce intestinal absorption of this drug; the evidence suggests it may be best to wait one hour after taking levothyroxine before drinking coffee (Benvenga, Thyroid 2008; American Thyroid Association).

Cruciferous vegetables such as broccoli, brussel sprouts and cabbage contain compounds that can interfere with thyroid function. However, these compounds appear to be deactivated in vegetables that are cooked (McMillan, Hum Toxicol 1986).


Learn More About Supplements and Thyroid Health



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COMMENTS

Margaret15560   September 23, 2017
When I was on prescription lithium some years ago, my thyroid medication dosage had to be increased. When that was discontinued, my thyroid medication needed to be decreased.

Virginia15550   September 18, 2017
I have used Ashwaghanda & bladderwrack for a year & my blood tests reveal a normal thyroid

Karen15625   October 3, 2017
That's great to hear. My experience with those two supplements have also been really positive--more stamina and energy.

Mike15528   September 13, 2017
Some patients on synthetic thyroid medications who are not doing so well on them, might consider Nature-throid or Armour thyroid, which is made from dessicated pig thyroid, contains several hormones, not just T4. Some patients do much better on this medication, and it's much cheaper, too.
But most doctors have to be pushed to prescribe it, and some do not know the conversion dose when changing from synthetic to the natural hormone.

Karen15552   September 20, 2017
I was on 88 meg of levoyhyroxin for several years. Blood work every 6 months revealed a decrease in T-3 and reverse T-3. I have been on 60 (mcg?) of Armour Thyroid for 60 days and feel SO much better. Coincidently, I have lost 7 lbs and 2.5% body fat without ANY CHANGE in diet or exercise. Blood work is scheduled in November so I will be interested to see new results.

Mary16264   December 4, 2017
I'm newly diagnosed and on 100mg of synthetic thyroid meds. Would love hear more about your progress. Good Luck

MaryJo16340   January 7, 2018
From much research and according to my naturalpathic doctor, Armour or Naturthroid is the better and healthier choice for thyroid help. It is my understanding that many experience side effects or little help on Synthroid, etc. I take 120 mg. Armour first thing in the morning, but often follow with coffee soon after. So I appreciated hearing the comments on holding off on coffee until later.

ruth17152   September 9, 2018
i am one of those people for whom Armour worked much better than synthroid

Marina15507   September 13, 2017
Because of extreme fatigue (I am diabetic) my endocrinologist increased my dosage of Synthroid. It did not help the condition, but caused palpitations. Thyroid tests alerted me -- and research indicated the dosage was responsible. I asked the doctor to lower my Synthroid to a previous level, and the palpitations ceased.
Several posts here speak of PALPITATIONS. I suggest they evaluate their Synthroid dosage. Can't hurt!

Dorothy13920   April 16, 2017
I recently spent six weeks in a rehabilitation facility. The nurse came around at 5:00 a.m. to administer Synthroid on an empty stomach. She came back at 7:00 with my meds for high blood pressure. I decided a two-hour separation between the two types of drugs is a good idea; it allows the thyroid hormone time to be fully absorbed in an empty stomach and get into the bloodstream. Back at home, I wake up several times during the night to go to the bathroom. If it's near 5:00 a.m. or shortly thereafter, I take Synthroid. Occasionally, I oversleep and take it much later. But I always wait two hours before taking my other meds and eating breakfast. Sometimes, I have a cup of coffee between 5:00 and 7:00, but I seem to have palpitations if I drink coffee a long time before eating food or taking blood pressure meds.

Elizabeth11679   February 12, 2017
I take Synthroid and need to discuss, with my endocrinologist, the time to take it. I get up at night to go to the bathroom, and was taking my Synthroid then. But I then got palpitations about four hours later. So I changed the time to take it, to after I got up. That stopped the palpitations, but I do like my morning coffee, so it's hard to wait an hour before coffee. And I'm not sure that's even enough time.

Diane11669   February 12, 2017
I take Synthroid and I am considering switching to a night dose. To take on an empty stomach, how much time is actually needed to wait after the last meal? I have heard several different times: 2 hours, 4 hours, 5 hours. ConsumerLab what is the standard?

ConsumerLab.com   February 12, 2017
Food has typically cleared the stomach within 2 to 3 hours.

Virginia 15327   July 26, 2017
My understanding is that one should take Synthroid in the morning on an empty stomach, at least 1 hour before food is introduced. My endocrinologist explained that the natural hormone it replaces begins about 4 A.M. as part of the circadian rhythm. So, we should try to mimic as closely as we can the body's natural rhythms. Taking it at night would be inferior to taking it in the morning. I suggest talking this over with your endocrinologist before you make this change.

Rebecca11316   October 2, 2016
After decades of stability, for the past few years, my thyroid tests have been up and down. varying up and down by about 25 mcg. Of course it was affecting how I felt as well, which was the worst part. I was having palpitations at night, and went from feeling manic to exhausted.

As it happened, I came across the following article about coffee interfering with thyroid medicine:

http://www.empr.com/case-studies/coffee-likely-culprit-in-patient-with-uncontrolled-hypothyroidism/article/494359/

After consulting with my doctor, I stopped taking the thyroid supplement in the morning with my coffee, and began taking it just before bedtime. Lo and behold, my thyroid needs went down, and I'm back to being at a stable dose of 150 mcg.

Good luck, and I hope this is helpful to others.


ConsumerLab.com   October 3, 2016
Thank you for making this point and sharing your experience with this, Rebecca. There is evidence that coffee can interfere with absorption of L-thyroxine (T4) (https://www.ncbi.nlm.nih.gov/pubmed/18341376).

G11619   January 25, 2017
Per my endocrinologist told me from the beginning that thyroid meds are to be taken first thing in the morning on an empty stomach, with water only. Then you must wait an hour before ingesting anything else such as other meds, supplements coffee and food. This hour is to give the thyroid meds time to fully absorb whereas these other things would interfere with proper absorption. After the hour you can take your other meds, supplements, coffee and food. An Endocrinologist will confirm this.

By the time I get to work an hour has passed and I can take my blood pressure meds and coffee, etc.

Kudos if you can take it at night but, if you do, you must make sure you have not had anything but water for several hours prior which is basically fasting. So, it seems like less of a hassle to wait until morning because you fast as you sleep. Peace and love.

Kim15322   July 26, 2017
A few years ago I read a study (by endrocrinologists) that showed taking Synthroid before bed resulted in better absorption. So I suggested to my mom that she switch, then she wouldn't have to wait for her morning coffee. Shortly after, she commented that she overall felt better taking it at night, and her lab work stabilized. The study didn't include Armour Thyroid, which is what I take, but I also switched to a bed time dose, because I'm a teacher (I can't wait an hour to get to work to eat breakfast and have coffee).

Joyce15492   September 10, 2017
I have found it simplified my routine to take my supplements in the morning with breakfast and thyroid medication right before bed (I refrain from late eating). It does not give me any sleeping problems.

Carol11620   January 25, 2017
I take my thyroid med immediatly upon wakening. I take about 1/2 hr getting showered, dressed etc & somwtimes longer if I go for a walk. I avoid calcium & mineral supplents until lunch time. I consistently have coffee or caffeinated tea with milk or cream with a small 'bite'. My MD says to do what I want, consistently, and he would adjust to the medication to get the right result. I've done this since starting levo in 2010. Now, my TSH remains stable ...usually between .5-1.0.However, my TSH levels were more solidly stable (more narrow range) once I switched to Tiroscint. I had stomach symptoms with dye free levothyroxine where with the Tiroscint I did not. I question if there is a relationship between fillers and absorption. As mentioned, I, too, become sleepless or sleep terribly if I take it before bed.

ann8354   January 13, 2016
I take Alpha Lipoic Acid for blood sugar and neuropathy and also Levothyroxin for Hashimotos Thyroiditis.
I make sure my vitamins and supps are taken by noon. Levo is taken on an empty stomach before I go to bed- an hour or more after eating.
There should be no interference and from my thyroid lab results, no problem at all. Be sure to take your Thyroid med on it's own and way after food etc is absorbed and processed,

Deborah11681   February 12, 2017
I added ALA to my regimen for neuropathy. Then my neurologist suggested CoQ-10; I am up to 200 mg twice daily. I cannot tolerate gabapentin or Lyrica. These two plus Deplin [methylfolate/active form of folic acid] do help but I am still opiate dependent. I also lack the MTHFR gene which has an essential enzyme for the conversion of B9 to a usable form. I take brand Synthroid. And prednisone. Because my sleep and eating patterns are all over the map, as was my TSH, we decided I would take my Synthroid with everything else I take in the AM because I usually eat at bedtime. That includes minerals, coffee, etc. But it works to keep TSH between .8 and 1.8. The less prednisone I am on the more Synthroid I need as it suppresses the antibodies at higher doses. Crazy dose now of 25 mcg 4x a week and 1/2 tab on Wednesday. Oy. It is a balancing act for sure.

X-tine8361   January 15, 2016
Many people, including my mother, experience insomnia when thyroid hormones--such as Levothyroxine--are taken at night before bed. In my mother's case, she found it helpful to take Levothyroxine immediately upon waking. To avoid any interference with thyroid hormone absorption, she takes nutritional supplements at least 4 hours later with lunch and dinner.

Barbara8474   February 23, 2016
Does Alpha Lipoic Acid help with peripheral neuropathy? I also am pre diabetic.

Marilyn11650   February 8, 2017
My heart doctor recommended alpha liopic acid for neurophy with my diabetics 2 and it helped me.

ConsumerLab.com   February 23, 2016
Hi Barbara - There is some evidence it may be helpful. See the "What It Does" section of the Alpha Lipoic Acid Supplements Review (https://www.consumerlab.com/reviews/_/alphalipoic/#whatitdoes) and this CL Answer (https://www.consumerlab.com/answers/_/nerve_pain_supplements/) for more information.

Jason114   August 25, 2014
If you follow the citation link regarding aLA and thyroid (single study done in Germany, 1991), only the abstract is available on PubMed. It does not mention the number of patients involved but does describe that aLA was given with T4. It is not clear if these were hypothyroid patients or "normals". If these were normal people, then decreasing the conversion of extra exogenous T4 to T3 may be a good thing.
Unfortunately, as with a lot of the reported benefits of supplements, there is a lot of maybes and mights with potential side effects as well.
Hopefully the FDA will one day get more involved and demand higher quality studies.

Ann11670   February 12, 2017
FDA wish they could get involved. When Congress evaluated whether FDA should regulate "nutritional" supplements, they decided nutritional supplements are probably safe and do not need to be regulated. Hence all of the problems with what's on the market today.

Rich84   August 6, 2014
The comments herein about alpha lipoic acid and acetyl L-carnitine indicate they are a hindrance, yet for a number of years they have been touted as wonderful supplements. I'm searching for the truth. Much of what I read about various supplements is contradictory from time to time.

Claudia11621   January 25, 2017
I find that for everything said to be wonderful to eat or take, someone else seems to say it is bad or harmful for some other other condition. It's confusing at best. My method is to make myself an experiment of one and see how it works for me. Others may get a totally different result.


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This CL Answer initially posted on 2/7/2014. Last updated 9/12/2017.
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