Explanation

Selenium (urine): what is measured?

The analysis measures how much selenium is excreted in the urine. Selenium is a trace element that is part of enzymes that protect cells against damage and that is needed for converting thyroid hormone. You get it from fish, meat, eggs, grains and especially Brazil nuts. The kidneys remove any excess, so the result mainly reflects your intake over the past few days.

What can it detect?

Selenium intake from food and supplements in the days before the measurement
An unusually high intake, for example from supplements or from a lot of Brazil nuts

Result

What does the result mean?

Selenium (urine) too high

A high value usually means that you are taking in a lot of selenium, for example from supplements or because you eat a lot of Brazil nuts; these contain much more selenium than other nuts. The kidneys remove the excess. Far too much selenium over a long period can cause symptoms such as brittle nails, hair loss, stomach and bowel symptoms and garlic-like breath, but in the Netherlands this hardly ever happens from food alone.

Selenium (urine) too low

A low value means that you took in little selenium in the days before the measurement, or that the urine was diluted. Selenium deficiency does not normally occur in the Netherlands. A low urine value is therefore no proof of a deficiency and on its own no reason to start taking supplements.

After an abnormal result

There is no standard follow-up. For a question about nutrition, the GP or a dietitian can look at your diet; with symptoms, the GP first looks for other, more common causes.

Reliability

How reliable is the test?

What an abnormal selenium excretion means for health has been little studied. Excretion mainly follows intake over the last few days and is not a measure of the amount of selenium in the tissues. A blood test says more about selenium status than a urine test. A single urine sample varies greatly with how much you drink and with what you ate the day before. That is why the result is usually corrected for the creatinine level, or urine is collected for 24 hours.

What can affect the result?

The result follows intake over the last few days, not the stores in the body.
Brazil nuts and supplements can raise the value sharply.
Fluid intake determines the concentration; without correction for creatinine, results are hard to compare.
There are no agreed cut-off values; the laboratory decides which limit it uses.

Who it is for

Who is the test useful for?

Useful for

In people without symptoms, a single value says little. For a specific medical question, for example with long-term nutrition through a drip or with a severe bowel condition, a blood test says more. A result in someone without symptoms is no reason to change your diet or start taking supplements.

How common is it?

In the Netherlands, selenium deficiency does not normally occur. Getting too much selenium from ordinary food is also difficult; only Brazil nuts contain a lot of it. Symptoms from too much selenium are rare in the Netherlands and are almost always linked to supplements.

Netherlands Nutrition Centre (Voedingscentrum) and the RIVM Dutch National Food Consumption Survey

Drawbacks and risks

A low result can wrongly lead to taking supplements, while selenium deficiency does not occur in the Netherlands and too much selenium is actually harmful.
A high result after eating Brazil nuts can cause unnecessary worry.

Get tested

Selenium (urine): test panels

Selenium (urine) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Urine
Selenium
Selenium in urine; for recent intake or exposure.
€ 42,00

Evidence

Sources

This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.

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