N-Methylhistamine/Creatinine [Mass Ratio], Urine
This urine test measures a histamine breakdown product relative to creatinine, helping evaluate mast-cell activation disorders.
["An elevated result may support increased mast-cell activity but must be interpreted with symptoms and other tests."]
Key facts at a glance
- LOINC
- 110386-0
- Short code
- Me-histamine/Creat Msmt Ur
- Synonyms
- Me-histamine/Creat Msmt Ur
- Category
- kidney
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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?
N-methylhistamine is a breakdown product of histamine. This test measures it in urine and compares it with urine creatinine, which helps account for differences in urine concentration.
Why might I need this test?
It may be used when symptoms suggest excessive histamine release, such as flushing, hives, swelling, abdominal symptoms, diarrhea, or bone pain. Providers may also use it when evaluating suspected systemic mastocytosis or another mast-cell activation disorder.
How is the test performed?
A urine sample is collected and tested in the laboratory. Depending on the order, this may be a single urine specimen or urine collected over a 24-hour period. The result is usually reported as a ratio of N-methylhistamine to creatinine.
How do I prepare for the test?
Follow the collection instructions provided by your clinician or laboratory, including whether a timed collection is required. Strenuous exercise, alcohol, acute illness, and certain medicines can affect results, so tell your clinician about relevant medications and recent health changes.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
An elevated N-methylhistamine-to-creatinine ratio may indicate increased histamine production or mast-cell activation. It can occur with systemic mastocytosis and other mast-cell disorders, but infection, exercise, or other factors may also raise the result. This test is interpreted together with symptoms, medical history, examination findings, and sometimes additional blood or tissue tests.
Short name
Urinary N-methylhistamine/creatinine ratio
Frequently asked questions
Does this test diagnose systemic mastocytosis?
Why is creatinine included in the result?
Can exercise or medicines affect the 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 16, 2026. · Read our editorial policy