Can serotonin be measured in the blood?

The neurotransmitter serotonin is associated with numerous bodily functions. In order to perform its many functions, the body must produce sufficient serotonin. This occurs largely in the gut, but also in the brain. Both a serotonin deficiency and a serotonin surplus can have a negative impact on health and well-being. Therefore, it is important to measure serotonin levels in case of complaints that may be related to serotonin. Currently, there are several methods available to measure serotonin in the body.

Can serotonin be detected in the blood?

Serotonin messen Blut

Yes, it is possible to measure serotonin levels in the blood. The family doctor can perform such a test. The serotonin level in the blood serum is measured. The reference range for serotonin in the blood is between 50 - 200 µg/l or 250 - 800 µg/1012 platelets [1]. This means that the levels of a healthy person are normally in this range.

Alternatively, it is possible to measure serotonin in urine. This is often done as part of a hospital stay, but is now possible at home with appropriate test kits. The tests make measuring serotonin in urine simple by sending a urine sample to a laboratory for professional evaluation.

Does measuring serotonin in the blood make sense?

Serotonin messen Körper

That depends on the purpose for which the serotonin level is to be determined. Anyone who wants to know whether their serotonin level in the brain is high enough will not gain any insights into this with a blood test. This is because there is many times more serotonin in the digestive tract and lungs than in the brain, and the serotonin in the blood cannot cross the blood-brain barrier. Therefore, the concentration of serotonin in the blood has little significance for the serotonin content in the brain. The blood-brain barrier is also the reason why serotonin is produced not only in the intestine but also in the brain, where the neurotransmitter also performs important functions.

To determine serotonin in the brain, a cerebrospinal fluid (CSF) puncture would have to be performed. However, such an examination is associated with many risks and is only performed in exceptional cases (and really only for research purposes and not for diagnosis).

Nevertheless, the serotonin level in the blood has clinical relevance, albeit in a different context. If it is elevated, this may be a sign of a carcinoid tumor. These tumors in the neuroendocrine system often increase the production of serotonin and other substances, resulting in elevated serotonin levels.

However, low serotonin levels in the blood have not yet had any clinical significance. It is possible, however, that this may change in the future as research identifies more links between serotonin in the blood and physical or mental illness.

Conclusion on serotonin measurement in the blood

It is possible to determine the serotonin content in the blood to obtain indications of a possible carcinoid tumor. With regard to depression or other mental illnesses, the serotonin value determined from the blood has no diagnostic value, since the messenger substance cannot pass the blood-brain barrier and therefore no statement can be made about the serotonin concentration in the brain.