Vitamins, minerals and amino acids
Selenium
Selenium in urine shows how much selenium you took in recently; it is not a measure of your selenium stores.
Everything about this testWhat it measures
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.
- 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
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.
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.
If your result is abnormal
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
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.
Limitations
- 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.
How common is this
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.
Who is this 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.
Downsides 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.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results