Tryptophan/Creatinine [Mass Ratio] in Urine
This urine test measures tryptophan relative to creatinine to assess how much tryptophan is being excreted by the kidneys.
["The result can help identify abnormally high urinary tryptophan excretion, which may occur with an inherited problem absorbing amino acids."]
Key facts at a glance
- LOINC
- 25139-7
- Short code
- Tryptophan/Creat Ur-sRto
- Synonyms
- Tryptophan/Creat Ur-sRto
- 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 amino acid, in urine compared with the amount of creatinine. Creatinine is used to account for differences in urine concentration.
Why might I need this test?
The test may be used to evaluate unusual urinary tryptophan excretion. It can help investigate certain inherited conditions that affect the intestine's ability to absorb amino acids, such as Hartnup disease.
How is the test performed?
A urine sample is collected and analyzed in the laboratory. The laboratory compares the urine tryptophan concentration with the urine creatinine concentration to calculate the ratio.
How do I prepare for the test?
Special preparation may not be needed for a random urine sample, but follow the laboratory's collection instructions. If a 24-hour collection is requested, collect all urine for the specified period and record the total volume. Tell your clinician about tryptophan supplements or other relevant medicines.
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.
An elevated urine tryptophan-to-creatinine ratio may indicate increased loss of tryptophan in the urine, including an inherited disorder of amino acid absorption such as Hartnup disease. Results can also vary with diet, supplements, kidney function, and urine concentration, so they should be interpreted with the other laboratory findings.
Short name
Urine tryptophan/creatinine ratio
Frequently asked questions
What does the urine tryptophan/creatinine ratio measure?
Why is creatinine included in this urine test?
What conditions can cause an elevated result?
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