Thyroid UK

When to take Selenium

I have decided to try a selenium supplement and have aquired a tub of Boots gel tabs which include vit A C and E. I'm not sure about the dose of selenium, it says 100 something, I think it's pg rather than mcg but it says one tab a day so it must be a reccommended dose. My question is when is the best time of day to take the selenium and how far apart from the thyroxine should I take it? I take my thyroxine first thing in the morning.

5 Replies

Hi HypoT2years, I take my Levo at night as it seem's to work better for me that way and then take my Selenium and Vit B etc in the morning so that I leave as much time as possible between the two. Just personal choice but I hope this helps. Perks


If it says mg that stands for milligram.

If it says mcg or ug that stands for microgram. There are 1000 mcg in a milligram.

If it says ng that stands for nanogram. There are 1000 ng in a microgram.

If it says pg that stands for picogram. There are 1000 pg in a nanogram.

The UK Food Standards Agency (FSA) recommends taking no more than 0.35 mg per day as a supplement.

That can also be expressed as 350 mcg.

If the label is showing 100 ng or 100 pg the amount is so small as to be utterly insignificant.

If you really care you will need to read that label properly.

There is no earthly reason to assume that a vitamin A, C and E supplement would or indeed should have any particular proportion of the daily requirement of selenium.

And I have no knowledge of when selenium should be taken in relation to thyroxine - but as always, take at least a couple of hours apart as even the fillers in some tablets can interfere with thyroxine absorption.



Hello Rod,

thanks for explaining what pg is, the only dosage I am familiar with is the mcg which is on the thyroxine.

I will ensure that I take the capsules a good few hours after my thyroxine.

I do really care about my own health but know that I need to do something for myself as well as taking the prescribed thyroxine as this does not seem to be restoring me to full health. I am working hard on the weight loss and just sometimess feel so very tired and unsure what else to do.

Do you think I should look for a higher dose selenium then? I have been very wary of starting on it at all due to the risks involved if too much is taken, so these gel tabs are most likely a good way of me trying this particular supplement.

I also take a chewable vit C 200mg and a vit B6 10mg.

Think I might print your conversion table off and try to get a bit more of an idea what to look for in dosage. Thank you for your help.

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I would have no worry at a low level - something like 25 mcg. But when people take larger amounts - like 200 mcg every day - I am then concerned that the amount is greater than needed and just might have unwanted effects. It probably would not matter much in the short term, especially if you are low on selenium already. But I am concerned about taking these higher doses long term.

Unfortunately there are few small dose tablets - so maybe taking 100 every other day, or splitting them (if possible) would be ways of using larger dose tablets to actually take low doses?

I am well aware that some people take much higher doses - even exceeding the FSA's 350 mcg per day limit - without appearing to fall over or suffer from obvious problems.

Maybe I would be less concerned if we actually knew what our selenium intake and current levels were when we started, and could monitor? But we can't.



I also take it at night as i take my euthyrox in the morning.. I take it with food.

With collagen peptides .far apart from my thyroid meds as most supplements seem to interfere with thyroid meds.

Hope that helps you.


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