Thyroid UK
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Could which of these supplements interact with Levothyroxine?

I take a huge number supplements due to a condition of mine, and was wondering which ones of them could interact with Levothyroxine. I thought I won´t be a bad idea to ask here.

Alpha-lipoic acid

Vitamin C

Vitamin D and Calcium


Coenzyme Q-10



Vitamin B complex


Vitamin E

And the medicines are....

Pantoprazole (very rarely; not a part of my daily routine)


Meloxicam (sometimes, like twice a year, I´ve to be put on a weekly course of it for neck pain, stiffness and inflammations)

So my question is, which supplements is it that could possibly interact with Levothyroxine and if some of them do, up to how many hours apart do I need to take them? I´m less worried about the other medicines though as Mirtazapine is the only one that is a part of my daily routine but I take it at bedtime, which translates into a difference of 13 hours between it and Levothyroxine.

3 Replies

Have you had a recent Full Thyroid Function Test? This would entail TSH, T4, T3, Free T3 and Free T4. Why I'm asking is that sometimes when we complain of symptoms that doctors decide we're depressed ) when it could be that our dose of levothyroxine (I'm assuming you are on levothyroxine) may be too low to provide the Active Hormone T3 which is required in our billions of receptor cells - the brain containing the most. Levothyroxine is inactive and it's job is to convert to T3.

If you read the question/answer dated September 24, 2002 on the folowing link may be helpful.

I am not medically qualified but I'd take supplements/vitamins about 4 hours apart from levothyroxine.



Most medications and supplements should be taken at least 2 hours away from Levothyroxine but iron, calcium and vitamin D should be taken 4 hours away.

If you Google Levothyroxine + [the name of the supplement or medication] interaction you should be advised of potential interactions.


There are (broadly) two ways in which interaction with levothyroxine occurs. The first is as the other substane is swallowed and goes through the stomach and intestine. The second is the impact the substance has on your body.

For the first issue, we have to be suspicious of almost everything - even if the active ingredient weren't a problem, the other inactive ingredients (excipients) might be. All too often there is simply no evidence either way as to whether there is an intereaction.

For the second issue, several of your other supplements/medicines could be an issue including selenium, Alpha Lipoic acid and L-carnitine. All three have effects on thyroid hormones in the body regardless of any possible interactions before being absorbed.

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