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Mary Shomon

Should You Take Your Thyroid Medication With Vitamin C?

By March 26, 2009

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In patients who take their thyroid medication but arenít able to achieve their target TSH level, researchers studied whether taking vitamin C along with levothyroxine medications (i.e., Synthroid, Levoxyl, Levothroid, etc.) could affect TSH levels. The results were quite surprising.

The research showed that taking vitamin C along with levothyroxine reduced TSH levels substantially, by as much as 27%. Taking the levothyroxine along with 1 gram of vitamin C mixed with water over a period of six weeks was able to help the majority of patients achieve their TSH target level. The researchers concluded that vitamin C can enhance oral absorption of levothyroxine, and taking vitamin C along with levothyroxine medications should be considered in patients with difficulties in the absorption of levothyroxine.

So, if you're not able to get your thyroid problem under control, talk to your doctor about the possibility of using supplemental vitamin C along with your thyroid medication.

Source: S. Licht et. al. ďDifficulties In The Absorption Of Levothyroxine: Improvement Using Vitamin CĒ Abstracts of the American Thyroid Association October 2008 Meeting, Online

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March 27, 2009 at 8:32 am
(1) Tanya N. says:

“The research showed that taking vitamin C along with levothyroxine reduced TSH levels substantially, by as much as 27%. Taking the levothyroxine along with 1 gram of vitamin C mixed with water over a period of six weeks was able to help the majority of patients achieve their TSH target level.”

Mary, Am slightly confused by the two sentences above… Is it that we should try taking Vitamin C with water for better absorption? Kindly adivse.

LOVE your work and thank you most sincerely for all the information and assistance you provide! Cheers, Tanya N.

March 27, 2009 at 9:45 am
(2) Val says:

I am very interested in learning more about this. I recently began adding iron supplements – taken with orange juice to aid absorbtion – because it was determined that my iron levels are low. Within weeks, my thyroid hormones rose quite dramatically – which previously had been very stable on block and replace therapy. (Treated for Graves disease).

When I then did research, I was suprised to find there were many articles that explained how low iron anemia could cause low thyroid hormones.

So, I’m wondering — was it really the Vitamin C that helped low the TSH (ie Raise thyroid hormone levels) OR, could the Vitamin C have helped absorb more iron, thus helping improve the anemia which in turn helped boost hormone levels?

It would be interesting to see if these people also had improved iron/ferritin scores…


March 27, 2009 at 10:31 am
(3) Mary Shomon / Thyroid Guide says:

Val, iron, if taken within 3 to 4 hours of thyroid medication, can prevent absorption of your thyroid medication.

So the first thing they should tell you is to take your iron at least 3 -4 hours apart from taking your thyroid medication.

Because if a thyroid patients on medication starts taking iron, it’s very likely that TSH will rise because your medication isn’t being absorbed properly — the iron is interfering bec. it’s being taken too close to the thyroid meds.

March 27, 2009 at 10:57 am
(4) judy says:

I am changing from Synthroid to Levo for financial reasons. The last time I attempted to make the change my Levo dosage needed to be increased each time blood work was drawn. Could taking the Levo now with Vitamin C be of help?

March 27, 2009 at 11:17 am
(5) Lisa Wilson says:

I see you said that Iron can interfere with absorption of thyroid medication. I always thought that was the same for calcium too. Have you heard of this or am I getting calcium confused with iron.

It is just that most Vitamin C powders have Vit C as calcium ascorbate in them. Do you think this will be a problem for absorption?

March 27, 2009 at 11:38 am
(6) Nancy says:

Mary, I totally agree with the above Vit C article. I take Vit C (1000-2000mg)daily every winter (oct-apr) and then stop taking it in the spring and my TSH level always changes. It goes from 1.7 to 2.5 and up. I just got my level tested last month and my level was really low .65(I’m still taking vitC) Of course, my endo doctor would never put that together.

Do you think that taking VitC at night with my calcium would change anything?

Thank you for all the information you provide. It is always extremely helpful. Nancy

March 27, 2009 at 4:15 pm
(7) Denise says:

Mary, does taking Armour and Vit C. create problems.
I take 2-3 thousand Mg of Vit C among other things daily. I never get colds, but we are having a hard time optimising my thyroid.
Thanks so much.

March 27, 2009 at 11:45 pm
(8) Val says:

RE: Taking iron

“Mary Shomon / Thyroid Guide says:
Val, iron, if taken within 3 to 4 hours of thyroid medication, can prevent absorption of your thyroid medication”

Hi Mary,

Thank you for responding. But I’m having the opposite effect. Ever since I started the iron my thyroid hormones (T4/T3) are rising. I have no TSH, so I can’t tell what is happening there. But my T4/T3 has come up considerably (which would mean my TSH – if I had any – was lowering).

I do take my Levo early in the morning and wait quite a long time before eating. My iron tablet isn’t taken until dinner time – usally 8-10 hours later – and with which I take the Vitamin C.

As I stated above, there is evidence that correcting iron deficiency anemia can help raise thyroid hormone levels (T4/T3), and since Vitamin C is what helps absorb iron too — my question was whether the iron being absorbed better was actually what helped these patients improve these hormone levels — as I experienced myself.

Best to you!

March 28, 2009 at 12:34 am
(9) kay says:

If iron levels are low and the thyroid is off, look for heavy metal toxins or toxicity that is affecting the whole body. The vitamin C link is often related to the immune system function.

March 30, 2009 at 10:00 am
(10) Karen says:

I take 125mcg of Levoxyl per day. So should I start taking a Vit. C supplement along with it or not?

March 31, 2009 at 11:56 am
(11) Ciara says:

Just so as you are all aware, considering that hypothyroidism affects women more than men, vit Cat levels like 1000mg is medically CONTRAindicated for any women taking the oral contraceptive pill as it interferes with the absorbtion of the pill. If you think badly absorbed tyroid meds is bad, imagine wht a disaster an unplanned/unwanted pregnancy would be! So this would NOT be recommended for most women up to age 50 or so, unless of course they were tryign for a baby.

April 1, 2009 at 3:19 pm
(12) Deborah Ross says:

Lisa, you are correct in that calium should not be taken with your thyroid medication. I had my thyroid removed and while doing so my parathyroids were severed which control calcium in the body. I have to take massive doses of calcium but have been told that I should take my thyroid medication four hours after I take my calcium. I have discovered trouble keeping my thyroid levels even because of my calcium which I have to take every 6 hours – so they overlap. It does interfere with my thyroid. Hope this helps.

April 2, 2009 at 7:41 am
(13) SV says:

It’s completely irrelevant how the TSH value changed in the people in the study. It has been proven in studies that the TSH value is not related to the degree of hypothyroidism symptoms.

The only thing that matters is if the hypothyroidism symptoms improved or disappeared with vitamin C, and this study (along with 99% of other hypothyroidism studies) is apparently not concerned with that so it is unfortunately worthless.

April 3, 2009 at 9:28 am
(14) elaine says:

I don’t think it is worthless. When my tsh is below a 1, I have hyper symptoms,when it is above 2, I have hypo symptoms. So there must be something to tsh levels. At least in me, I notice a difference in how I feel directly related to my tsh level.

April 7, 2009 at 5:48 am
(15) Jaime B says:

I have no thyroid, it just died on me 25 yrs ago, I have seen many doctors thru the yrs, until recently no doctor would up my dosage I took 125mg for 25 yrs and yes feeling alful all the time but I found an endo who listened and put me on armour, its been 9 mths and I do feel better but I noticed thru the winteer I am still pretty stiff, joints hurt but when it warms up I feel much better, the endo did up my med to 150mg, still working on the dosage, but I would like to see more articles on people who do not have thyroids, how we can get more help from med and suppliments, anything to help matabolism, even after 25 yrs, I still don’t understand about all the levels, and would it help to take vit c for people who have no thyroid. thanks jaime

April 10, 2009 at 11:01 am
(16) Alyce says:

I am interested in this because I cannot get my TSH levels under 6. I have had surgery, half of thyroid left, but TSH levels all over and I have Heart Failure. Cardio wants levels down, but on high dosage of Levothroid, I have heart palpitations and feel awful, on lower dosage, no heart palp, but also no energy. The question is should the liquid C be taken at the same time as my Levothroid or at least a half hour later? Could Mary answer that as the article was unclear. Thanks, Alyce

April 16, 2009 at 1:30 am
(17) Tish says:

I am not surprised by these results. I found by accident 10 yeras ago that taking 500mg of Vit C each night cut my thyroid antibodies from over 25,000 down 6,000 and eliminated many symptomes of Hashimoto’s. As soon as I stopped taking it all the levels rose and symptoms returned.

April 21, 2009 at 6:00 pm
(18) Lori says:

I have the same question as above about taking vitamin C with Armour. I have had problems with absorbtion. Will taking vitamin C with Armour help me? Thank you.

May 6, 2009 at 10:33 am
(19) Jeannette says:

I take my Synthroid 175 at night and have done so for years,
As to the Vit C I recently started taking 500 mgs Vit C at night with my synthroid, as a result of Mary’s newsletter. I had previously taken it in AM. the results were immediate, my hair and nails grew faster than usual. After 4 weeks I decided to half the vit C until I can get in and have my blood levels checked. I also feel more energy!

Thanks for all the good advice.

September 6, 2009 at 4:19 pm
(20) DJ says:

That’s great news Jaime. I can’t find a doctor, not even an endo, who will change my medication even though I have numerous complications indicating an under-active thyroid. All of their solutions are for me to go see individual doctors (for each problem) and then be treated for them separately, when all that needs to be done is a minor dose increase.

I am seriously concerned by the stupidity of doctors. Especially when one of them tells me something that happened to me was impossible. Then I go online and see that it was used for the exact same thing with other people. So obviously, it’s not impossible.

I just started taking Vitamin C. Not for this reason but, was looking up whether it was safe to take at the same time as my Thyroid medication and found this article. Thanks for the info. Maybe it will help with the problems I’m having with my Thyroid as well. :)

It has certainly NEVER been recommended by a doctor for any of the reasons why I should be taking it.

October 26, 2009 at 10:06 am
(21) Carol says:

Can taking to much Vit C cause kidney stones?

February 13, 2010 at 6:59 pm
(22) Lisa says:

I agree with Tish. My tsh levels were 4.7 and antibodies were 191 – I felt flu-y all the time. I started taking 1000mg Vit C about 2 years ago and symptoms decreased. My last blood test showed tsh at 4 but unfortunately GP wont authorise antibody test. I’ve recently not taken vit c for about 2 weeks and symptoms are starting to come back. Hence I have quickly bought some more and definitely wont stop again

February 21, 2010 at 7:04 pm
(23) Olga says:

Hi Mary:

I too have noticed that my TSH levels have improved on Vitamin C. I found this paper that you might find interesting. Believe it or not it’s from 1975!


They found that vitamin C deficiency and throid problems are related. Some thyroid problems may infact be an early symptom of scury, which is caused by vitamin C deficiency.

January 1, 2011 at 11:04 am
(24) Sarah says:

I’ve been reading all of these comments and noticed that Mary hasn’t responded to any since March 2009, almost two years ago. Does she still work here? These are some really important comments and questions. I thank everyone for sharing their experiences. I have been on synthroid for years and still have trouble with energy and weight. I am going to try taking it at night with Vitamin C. I also find that I get anemic (low-iron) during my period which has gotten very heavy in the last few years. So I am going to try adding iron supplements in the morning and see what that does. Any thoughts or suggestions about that? I welcome them. Thanks!!

January 1, 2011 at 2:37 pm
(25) Mary Shomon / Thyroid Guide says:

There are thousands of blog posts dating back years, and this one was posted in 2009, and I don’t often get a chance to respond to comments on older posts. As of Jan 1, 2011, I am still here — posting new blog posts and articles, doing the weekly newsletter, writing my books, etc.

To recap — the point was that taking the levothyroxine, with vitamin c — with the vitamin C in water (powdered vitamin C) — all at the same time, helped with absorption of thyroid medication.

Calcium, like iron, can interfere with absorption of thyroid medication.

Re: those who want to know if they should start taking Vitamin C, that’s something your doctors will need to advise, and if you do decide to do that, be sure to have the thyroid levels rechecked after you start, in case it affects your thyroid levels.

Sarah — having problems with enregy and weight while on Synthroid is common. I suggest that you read the latest series on Optimizing Hypothyroidism Treatment, from some of the nation’s top practitioners, for ideas on improvements to your treatment.

July 26, 2011 at 7:29 pm
(26) mary says:

Is it okay to take Ginger along with Levoxyl for hypothyroidsm?

December 19, 2012 at 5:24 pm
(27) Hope says:

Still, the question is-does it improve absorption or just lower TSH? Metformin lowers TSH but not because of increased absorption–it simply acts on the TSH secretion-which can be very problematic if free t4/t3 are not also tested.

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