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Signs of excess selenium

Lots of people here take selenium. Whilst this is a valuable supplement if you are lacking, there are limits and unpleasant effects of taking too much. The level of selenium when this happens is quite low so if you have any of these symptoms, cut back.

The Office of Dietary Supplements reports that high levels of selenium in your blood, defined as a concentration of more than 100 micrograms per deciliter, causes selenosis. The symptoms of selenosis include fingernail loss, skin rash, hair loss, weight loss, fatigue and irritability.

5 Replies

This is a great post as so many people take without testing levels first.

The same with iodine.

Bit worrying.


Thanks for this. I didn't realise that selenium could be a problem. My nails have started to develop pitting and ridges. I've been taking selenium for months. I'll stop now and consider a test from Medichecks.


Testing is always a good practice; however, tests are far more accurate prior to supplementation; so, to establish the baseline. Once you have been supplementing and getting tested, it gets far more complicated for certain vitamins and minerals

The most common signs of selenium toxicity are garlic breath, vomiting, and diarrhea.

Whereas nails discoloration with ridges are also listed as signs of selenium toxicity they can be due to many other things such as illnesses, other deficiencies such as iron and zinc, or simply aging.

Before you get unnecessarily alarmed about your selenium's, and of course until you have your test done and get your results, it all depends on how much you have been supplementing.

The recommended daily dose for Hashimoto's is 200 mcg per day and for 6 months so to lower the antibodies. At times, you need a more extended time for supplementation as it is all depending on your absorption rate. Then, for maintenance 100 mcg daily.

The upper limit, quoting Dr Izabella Wentz and WebMed is 400 mcg/day.

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A few years ago we used to see recommendations all over, and products, at 400 micrograms a day.

More recently, 100 and 200 micrograms have become much more common.

Given that 800 micrograms a day is usually regarded as "too much", I consider even 400 as a supplement is a lot. After all, you will be taking in some in your diet anyway.


I had my selenium tested by gp before supplementing. I was top of the range! So no supplements for me! I would always encourage testing first. Zinc & copper excess can be a problem too.


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