Urine
Iron
Iron in urine; excretion (supplementary to iron status).
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Iron · Urine
Iron (urine)
Iron in urine says virtually nothing about the iron stores; the body hardly excretes iron through the kidneys.
At a glance
- Measured in urine
- In 1 test panel
- No special preparation
Explanation
Iron (urine): what is measured?
The analysis measures how much iron is excreted in the urine. The body is sparing with iron: most iron is reused and only a very small amount is lost each day, mainly through shed gut and skin cells and, in women, through menstrual blood. Normally virtually no iron leaves the body through the urine. The result therefore says something about excretion and not about the amount of iron you have in store.
What can it detect?
- An unusually high iron excretion in the urine, for example when red blood cells break down in the bloodstream or during treatment with a drug that binds iron
Result
What does the result mean?
Iron (urine) too high
A raised value is rare. It may fit breakdown of red blood cells within the bloodstream, in which hemoglobin and iron end up in the urine, or treatment with a drug that binds iron and removes it through the kidneys. Damage to the kidney tubules can also increase excretion. A raised value does not mean you have too much iron in your body.
Iron (urine) too low
A low or unmeasurable value is normal and expected. The body hardly excretes iron through the kidneys, so a low result says nothing about iron deficiency. If you want to know whether there is an iron deficiency, you need ferritin in blood, possibly together with hemoglobin and the transferrin saturation.
After an abnormal result
With a question about iron deficiency or iron overload, the GP measures ferritin and, if needed, hemoglobin and the transferrin saturation in blood. An abnormal urine iron on its own does not lead to any standard further testing.
Reliability
How reliable is the test?
Iron in urine says nothing about the iron stores, because the body hardly excretes iron through the kidneys; the meaning of an abnormal value has been little studied. For iron status, the Dutch GP guideline (NHG) on anemia and the Dutch Society for Clinical Chemistry (NVKC) rely on blood tests: ferritin, hemoglobin, transferrin and the transferrin saturation. A single urine sample varies strongly 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 over 24 hours.
What can affect the result?
- The body hardly excretes iron through the kidneys; the measured amounts are close to the lower limit of the measurement.
- Fluid intake determines how concentrated the urine is; without correction for creatinine, results are hard to compare.
- Blood in the urine, for example from menstruation or a bladder infection, can raise the result strongly.
- There are no agreed cut-off values; the laboratory decides itself which limit it uses.
Who it is for
Who is the test useful for?
Useful for
A result only really means something for a specific question, such as breakdown of red blood cells in the bloodstream. In people without symptoms, iron in urine adds nothing to the picture of iron status. If you suspect you have an iron deficiency or, on the contrary, iron overload, you need ferritin and the transferrin saturation in blood.
How common is it?
Iron deficiency is the most common cause of anemia in the Netherlands, especially in women who menstruate. That deficiency is diagnosed in blood and not in urine. Conditions in which iron appears in the urine are rare.
The Dutch GP guideline (NHG) on anemia and the NVKC
Drawbacks and risks
- A low result can wrongly be read as iron deficiency, or a high result as iron overload; both require blood tests.
- An abnormal result without agreed cut-off values to interpret it easily leads to unnecessary further testing.
Get tested
Iron (urine): test panels
Iron (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.
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.
More about risks and resultsMore explanations
Other tests: Iron
- Ferritin
- Iron
- Soluble transferrin receptor (sTfR)
- TIBC (total iron-binding capacity)
- Transferrin
- Transferrin saturation