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Mercury in blood shows how much mercury you have taken in over the past weeks, usually through fish.
Everything about this testWhat it measures
The analysis measures how much mercury is in your blood at this moment. The body does not need mercury and does not use it for anything. Mercury occurs in small amounts in the environment and in food, especially in fish and shellfish. The value in blood mainly reflects exposure over the past weeks.
- Recent exposure to mercury, for example from eating a lot of fish or shellfish
- Exposure through work or through an accident with mercury, for example a broken mercury thermometer or barometer
High
A raised value means that you have taken in more mercury than average. For most people in the Netherlands, this is due to eating a lot of fish or shellfish. The level of the value does not tell exactly how much mercury someone has taken in. A raised value without symptoms does not mean there is damage. Symptoms that can go with real mercury poisoning are tingling in the arms and legs, trembling, worse vision or hearing, and kidney problems.
Low
A low or unmeasurable value is normal and occurs in most people. The body does not need mercury, so a low result is not a deficiency and does not call for supplementation. A low value does not rule out exposure long ago, because mercury in blood mainly shows the last few weeks.
If your result is abnormal
With a raised result, the GP first looks for the source, for example fish consumption or work, and has the measurement repeated after a few weeks if needed. If real poisoning is suspected, referral follows to a doctor with knowledge of poisoning, for example through the occupational physician or an internist (specialist in internal medicine).
Reliability
Mercury in blood is mainly informative with a known exposure or with symptoms that fit mercury poisoning; in people without known exposure, a single value says little. According to the Dutch Society for Clinical Chemistry (NVKC), the level of a raised value does not tell how much mercury someone has taken in. The result says something about exposure, not about a buildup that you can remove with a course of treatment. Laboratories use different methods and reference values, so results from different labs cannot simply be compared.
Limitations
- Fish, shellfish and seaweed in the days before the blood draw can temporarily raise the value.
- Blood mainly reflects the last few weeks; exposure from years ago can no longer be seen in it.
- Organic mercury from fish and inorganic mercury from vapor behave differently in the body; most laboratories measure the total and do not make that distinction.
- There are no agreed cutoff values; the limit between normal and raised comes from the laboratory itself.
How common is this
Mercury poisoning is rare in the Netherlands. At home, mercury is mainly released when an old thermometer, barometer or blood pressure monitor breaks, or with a broken energy-saving lamp or fluorescent tube. Exposure through work has become uncommon because of strict rules.
Who is this useful for
Useful with a known exposure, for example after an accident with mercury or with work that involves mercury, and with symptoms that suggest mercury poisoning. In people without symptoms and without known exposure, the measurement adds nothing. A result within the range the laboratory calls normal does not mean that existing symptoms are thereby explained or ruled out.
Downsides and risks
- A slightly raised value in someone without symptoms easily leads to worry and to follow-up testing or treatments that change nothing for your health.
- The result can wrongly be seen as the explanation for vague symptoms, so that another cause is found later.
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