Selenium toxicity hair loss: what a 201-person outbreak showed

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Hair loss and nail brittleness are the most common signs of chronic selenium excess (NIH ODS), and in a 2008 outbreak caused by a supplement with 200 times its labelled selenium, 70% of 201 cases lost hair — a median of 50% of scalp hair — and 29% still had hair loss 90 days later.

No consistent week-by-week window is published for this, so it is not on the calculator.

The 2008 outbreak in numbers

Measure	Result
Product	Liquid supplement with ~200× the labelled selenium (40,800 µg per ounce) [JAMA]
Cases	201 in 10 states [JAMA]
Hair loss	70%; median 50% of scalp hair lost; 18% of those reporting lost all scalp hair [JAMA]
Still losing hair at ≥90 days	29% [JAMA]
Median time on the product	29 days [JAMA]

The limits

The US Tolerable Upper Intake Level for adults is 400 mcg a day, set from the amounts linked to hair and nail loss [NIH].
Selenium-only supplements typically contain 100 to 400 mcg [NIH].

Normal vs. warning signs

Commonly normal

Mild shedding unrelated to supplements — most hair shedding has another cause

Warning signs — get checked

Hair loss with brittle or discoloured nails
Garlic-smelling breath
Diarrhoea, fatigue or tingling
Taking several products that each contain selenium

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What may help

Add up selenium from every supplement you take and compare it with 400 mcg a day.
Bring all your supplement bottles to your doctor.
Ask about testing if you have hair and nail changes together.

Related triggers

Supplements

Telogen club hair

Frequently asked questions

Can too much selenium cause hair loss?

Yes — NIH ODS says hair loss and nail brittleness are the most common signs of chronic excess.

How much selenium is too much?

The US upper limit for adults is 400 mcg a day.

Does selenium hair loss grow back?

In the 2008 outbreak, 29% still had hair loss 90 or more days after stopping the product.

Sources

NIH Office of Dietary Supplements. Selenium — Health Professional Fact Sheet
JAMA Internal Medicine, 2010. Acute Selenium Toxicity Associated With a Dietary Supplement (201 cases)