How To Test Selenium Levels (My Five-Point Selenium Checklist)

Apr 13 / Drs. Bryan & Julie Walsh

Selenium is a critically important, yet often misunderstood element.

On the one hand, selenium has many important roles having to do with proper immune system function, glucose regulation, reproduction, mood, cancer prevention, as well as for optimal functioning of specific selenoenzymes necessary for proper thyroid hormone synthesis and glutathione use.

On the other hand, selenium is said to have a ‘narrow therapeutic window’, and according to research, exceeding this optimal intake level might lead to some of the very same issues selenium deficiency prevents.

Despite this narrow window between deficiency and excess, clinicians and practitioners are quick to recommend selenium supplementation to their patients for its antioxidant, anti-inflammatory, thyroid-improving, and glutathione-boosting properties.

This is problematic and could cause patients more harm than good.

As part of this research, we took a close look at a popular Hashimotos protocol designed by a major nutraceutical company and found the selenium content from all the supplements combined to be almost 20 times the RDA for selenium!

What does that mean? Practitioners who are depending on these protocols to help their patients may be causing additional issues instead.

If too little selenium is bad, too much is toxic, and the difference between the two is narrow, how can we as practitioners know who needs extra selenium and who doesn’t?

One answer is testing, and we should probably be doing more of it if we’re recommending selenium as a supplement, or if it is in supplements we’re giving.

There are many ways of testing selenium status – blood, hair, urine, stool, and even toenails – each having pros and cons, and various levels of accuracy.

People debate about the accuracy of various types of selenium testing but the reality is, using serum to determine selenium levels is good enough. It is easily the most often used test in research studies around the world, generally correlates with intake, and is, therefore, the most useful tissue and test for evaluating selenium status. The fact that it is so often used also helps give us insight into what optimal levels are for most people.

A bit of caution is required when interpreting serum selenium, however. According to some reports, selenium is a negative acute phase reactant, which means it can decrease during periods of inflammation. This simply means that when running serum selenium, take a quick look at albumin, and CRP if you have it. If albumin is also low, or CRP is high, then serum selenium might not be a good indication of selenium status. But if those other markers are normal, then serum selenium is a good indicator of overall selenium status.