Explanation

Serotonin (blood): what is measured?

Serotonin is a signaling substance. In the brain it plays a role in mood and sleep, but most of the serotonin in the body is made in the gut wall. In the blood, more than 90 percent of it is in the platelets. This analysis measures serotonin in serum: when the blood clots, the platelets release their serotonin. Serotonin from the brain barely reaches the blood; the value therefore mainly says something about the gut, diet and the platelets.

What can it detect?

The effect of serotonin-rich food, such as banana, pineapple, walnut, tomato and avocado
The effect of medicines that act on serotonin, especially antidepressants (SSRIs), which strongly lower the serotonin in the platelets
Rarely: a hormone-producing tumor in the gut or lung (neuroendocrine tumor) that makes a lot of serotonin

Result

What does the result mean?

Serotonin (blood) too high

A raised value is usually caused by food in the days before the blood draw, such as banana, pineapple, walnut, tomato, avocado, plums or melon, or by supplements with 5-HTP or tryptophan. A high platelet count also raises the value. A high value does not mean there is more serotonin in the brain and says nothing about your mood. Rarely: a strongly raised value fits a hormone-producing tumor in the gut or lung (neuroendocrine tumor, formerly called carcinoid); this single measurement is not intended for that, and diagnosis takes place in hospital with other tests.

Serotonin (blood) too low

A low value is most often caused by antidepressants such as SSRIs: they make the platelets take up little serotonin, so the value in blood falls sharply. A low platelet count also lowers the value. A low value does not mean there is a shortage in the brain and is not a sign of depression or a 'serotonin deficiency'.

After an abnormal result

With a raised value, the GP first looks at diet, supplements and medicines in the days before the blood draw and, if needed, repeats the test under the right conditions. If the value stays strongly raised, referral to an internist for further testing may follow.

Reliability

How reliable is the test?

Serotonin in blood cannot be used to assess mood, depression, anxiety or sleep: the brain and the blood each have their own serotonin, which barely exchange. According to the Dutch Society for Clinical Chemistry (NVKC), the result depends strongly on diet, age, sex and method, and every laboratory has its own normal values. Outside a specific medical question from a treating doctor, a result is hard to interpret.

What can affect the result?

Diet: the laboratory asks you not to eat pineapple, eggplant, avocado, banana, red currants, gooseberries, melon, mirabelle plums, plums, tomatoes or walnuts for 3 days before the blood draw.
Medicines: antidepressants (SSRIs) strongly lower the value. According to the laboratory, chlorpromazine and methocarbamol, among others, affect the measurement, and paracetamol (acetaminophen) and acetylsalicylic acid (aspirin) are advised against for 2 days beforehand. Do not stop a prescribed medicine on your own.
The blood must be centrifuged immediately after clotting and the serum frozen; if not, the value changes.
The platelet count partly determines the result.

Preparation

For 3 days before the sample is taken, do not eat pineapple, eggplant, avocado, bananas, red currants, melon, mirabelle plums, gooseberries, tomatoes, walnuts or plums; they raise serotonin.
Do not take acetaminophen (paracetamol) or aspirin (acetylsalicylic acid) for 2 days before the sample is taken. If they were prescribed to you, check with your doctor first.
Taking chlorpromazine or methocarbamol? Do not stop on your own, but mention it when your blood is taken.

Who it is for

Who is the test useful for?

Useful for

Useful if a treating doctor asks for this test as an addition to other tests. Not useful for assessing mood, depression, anxiety, sleep problems or a supposed serotonin deficiency, or for checking whether antidepressants or supplements work: the value says nothing about that. People who take antidepressants usually have a low value.

How common is it?

No condition is diagnosed with this single test, so there is no figure for how often an abnormal result means something. Abnormal values due to diet and medicines are common; tumors that make a lot of serotonin are rare.

NVKC, allesovertesten.nl

Drawbacks and risks

An abnormal value due to diet or medicines can cause unnecessary worry and unnecessary follow-up tests.
The result can wrongly be read as a measure of mood or as a reason to take supplements or change medicines.

Get tested

Serotonin (blood): test panels

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

Blood draw
Serotonin (blood)
Measures serotonin in serum, which comes mainly from the platelets. For anyone whose doctor asks for this test; the value says nothing about your mood.
€ 67,00

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.

More about risks and results

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