Understanding Lab Tests for Carcinoid Syndrome
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
Carcinoid syndrome is a rare condition that occurs when carcinoid tumors release excessive amounts of hormones, particularly serotonin, into the bloodstream. This hormonal excess can cause a variety of symptoms including flushing, diarrhea, wheezing, and heart problems. Blood tests play a crucial role in diagnosing this condition by measuring elevated hormone levels.
Recommended Test
Serotonin, Serum
This test measures serotonin levels in the blood, which are typically elevated in carcinoid syndrome. High serotonin levels can indicate the presence of carcinoid tumors that are actively releasing this hormone into the bloodstream, causing the characteristic symptoms of flushing, diarrhea, and potentially heart complications.
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Diagnosing Carcinoid Syndrome
Because carcinoid syndrome symptoms can mimic other conditions, laboratory testing is essential for accurate diagnosis. The syndrome is characterized by the overproduction of certain hormones and bioactive substances by neuroendocrine tumors, making blood tests a primary diagnostic tool for detecting these elevated levels.
Understanding Your Results
Elevated serotonin levels in the blood can be a strong indicator of carcinoid syndrome, especially when accompanied by typical symptoms. However, test results should always be interpreted in conjunction with clinical symptoms and other diagnostic findings. Additional imaging studies may be recommended to locate the source of hormone production.
Important Considerations
The information here is for educational purposes only and is not a substitute for professional medical advice. Always consult with a healthcare provider for diagnosis and treatment. Early detection and monitoring of carcinoid syndrome through appropriate testing can help guide treatment decisions and improve patient outcomes.
