5-Hydroxytryptophan (5-HTP) plasma concentration (24-hour profile)
This test measures the amount of 5-hydroxytryptophan, a natural compound involved in serotonin production, over a 24-hour period in your plasma. It may be used to assess serotonin synthesis or evaluate conditions linked to serotonin metabolism.
["This test helps track serotonin-related pathways, often used in research or specialized clinical contexts."]
Key facts at a glance
- LOINC
- 23943-4
- Short code
- Xylose 2h p Xyl PO Bld-mCnc
- Synonyms
- Xylose 2h p Xyl PO Bld-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 20
- Ref high
- 400
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82670
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms or conditions suspected to involve serotonin dysfunction, such as certain mood disorders, gastrointestinal issues, or metabolic studies. It could also be part of a broader evaluation for rare metabolic or neurological conditions.
What to Expect Before the Test
No special preparation is typically required, but you may need to fast for a portion of the 24-hour period, depending on your protocol. Follow your healthcare provider’s instructions carefully to ensure accurate results.
How the Test Works
Blood samples will be collected at specific intervals over 24 hours to measure 5-HTP levels in your plasma. The samples are then analyzed using a specialized laboratory technique to determine the concentration of 5-HTP at each time point.
What the Results Mean
Interpreting results requires medical expertise. Elevated or altered patterns may indicate abnormal serotonin metabolism, while normal ranges suggest typical function. Your provider will discuss findings in the context of your health and symptoms.
Reference range
Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
24-Hour 5-HTP Profile
Frequently asked questions
What could cause abnormal results?
How often should this test be repeated?
Is this test covered by insurance?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy