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Test Code MISC2MAYONMHIN N-Methylhistamine, Urine

Reporting Name

N-Methylhistamine, U

Useful For

Screening for and monitoring of mastocytosis and disorders of systemic mast-cell activation, such as anaphylaxis and other forms of severe systemic allergic reactions


Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis

Profile Information

Test ID Reporting Name Available Separately Always Performed
NMH N-Methylhistamine, U No Yes
NCTU Creatinine Concentration No Yes

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Advisory Information

Individuals who are taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine would have increased N-methylhistamine (NMH) results, which would be uninterpretable.

Specimen Required

Supplies: Aliquot Tube, 5 mL (T465)

Container/Tube: Plastic, 5-mL tube

Specimen Volume: 5 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. No preservative.

Additional Information:

1. 24-Hour collection is preferred, but a random specimen is also acceptable.

2. See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.

Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 8 days
  Frozen  14 days
  Ambient  24 hours

Reference Values

0-5 years: 120-510 mcg/g creatinine

6-16 years: 70-330 mcg/g creatinine

>16 years: 30-200 mcg/g creatinine

Day(s) and Time(s) Performed

Tuesday, Thursday; 10 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
NMHIN N-Methylhistamine, U 44340-8


Result ID Test Result Name Result LOINC Value
NCTU_ Creatinine Conc 20624-3
21589 N-Methylhistamine, U 44340-8
TM73 Collection Duration 13362-9
VL63 Urine Volume 3167-4

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Method Name

NMH: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

NCTU: Enzymatic Colorimetric Assay

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.







50% Acetic Acid


Boric Acid


Diazolidinyl Urea


6M Hydrochloric Acid


6M Nitric Acid


Sodium Carbonate