Serotonin Testing: What It Tells Us About Mood and Mental Wellness

Written by Kristy Beard, MSN, APRN, FNP-C — Board-Certified Family Nurse Practitioner and Founder of Elevate Health and Wellness, serving patients across the Gulf Coast in Gautier, MS and Foley, AL.

What Is Serotonin?

Serotonin (5-hydroxytryptamine or 5-HT) is a monoamine neurotransmitter synthesized primarily from the amino acid tryptophan. While it is often described primarily in the context of mood regulation, approximately 90 to 95% of the body's serotonin is produced in the gastrointestinal tract — where it regulates intestinal motility, secretion, and the gut-brain axis. The remaining 5 to 10% is produced in the brain, where it influences mood, sleep, appetite, cognitive function, and the modulation of pain perception.

What Does a Serotonin Blood Test Actually Measure?

A serum serotonin test measures the concentration of serotonin in the blood — predominantly the serotonin stored in platelets, which take it up from the gastrointestinal tract. This is an important distinction: serum serotonin does not directly measure brain serotonin levels, which are separated from the peripheral circulation by the blood-brain barrier. Brain serotonin activity cannot be measured directly through a blood test with current technology. This means that a serum serotonin level is most useful for evaluating conditions involving peripheral serotonin production and metabolism — particularly neuroendocrine tumors (carcinoid tumors) that produce excess serotonin — rather than as a direct diagnostic marker for depression or anxiety.

When Serotonin Testing Is Clinically Useful

At Elevate Health and Wellness, Kristy Beard, MSN, APRN, FNP-C orders serotonin testing in specific clinical contexts where peripheral serotonin measurement provides actionable information. These include evaluation of suspected carcinoid syndrome, characterized by flushing, diarrhea, and wheezing; assessment of gastrointestinal motility disorders where serotonin dysregulation is a contributing mechanism; and as one component of a broader functional evaluation of the gut-brain axis in patients with concurrent GI and mood symptoms.

How Elevate Evaluates Mood and Mental Wellness Comprehensively

For patients presenting primarily with depression, anxiety, or mood instability, Kristy takes a comprehensive approach that extends well beyond a single serotonin test. A thorough mental wellness evaluation at Elevate includes thyroid function assessment (thyroid dysfunction is one of the most common and most treatable causes of depression and anxiety), hormone panel evaluation (estrogen and progesterone fluctuations directly affect serotonin receptor sensitivity and neurotransmitter production), vitamin D and B12 levels (both are essential for neurological function and mood regulation), inflammatory markers (chronic inflammation dysregulates the hypothalamic-pituitary-adrenal axis and impairs neurotransmitter synthesis), and blood sugar regulation assessment (glycemic instability produces significant mood and cognitive effects).

Ready for a comprehensive mental wellness evaluation? Learn about our primary care and lab services at Elevate in Gautier, MS and Foley, AL.

Sources: NIH. Serotonin and Mental Health. ncbi.nlm.nih.gov. | American Psychiatric Association. Depression Evaluation Guidelines. psychiatry.org.

This article is written by Kristy Beard, MSN, APRN, FNP-C, board-certified Family Nurse Practitioner and founder of Elevate Health and Wellness. Information provided is for educational purposes only and does not constitute medical advice. Please consult a licensed healthcare provider for personalized care.