Tryptophan/Creatinine Ratio, 24-Hour Urine
Measures urinary tryptophan relative to creatinine in a 24-hour collection, helping evaluate tryptophan excretion and identify reduced absorption or abnormal metabolism.
["This test measures how much tryptophan is being lost in urine compared with creatinine."]
Key facts at a glance
- LOINC
- 44414-1
- Short code
- Tryptophan/Creat 24h Ur
- Synonyms
- Tryptophan/Creat 24h Ur
- Category
- kidney
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- 0.5 N/A – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test measures the amount of tryptophan, an essential amino acid, in urine collected over 24 hours. The result compares tryptophan with creatinine, a muscle waste product, to help account for differences in urine concentration and collection amount.
Why might I need this test?
It may be used to evaluate nutritional status or investigate increased tryptophan loss in urine. An elevated result can occur with reduced intestinal absorption, certain inherited disorders of amino acid transport, or other conditions that affect tryptophan metabolism.
How is the test performed?
You collect all urine for exactly 24 hours, beginning and ending at the specified times. The laboratory measures tryptophan and creatinine in the collection and reports the amount of tryptophan relative to creatinine.
How do I prepare for the test?
Follow the collection instructions provided by your healthcare professional or laboratory. Empty your bladder at the start time, collect every subsequent urine sample for 24 hours, and record when the collection ends; ask about refrigeration and storage requirements.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
24-Hour Urine Tryptophan/Creatinine Ratio
Frequently asked questions
Why is creatinine included in the result?
What conditions can cause increased urinary tryptophan?
Can I collect a 24-hour urine sample at home?
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 17, 2026. · Read our editorial policy