Ordering Recommendation

Aids in the evaluation of patients with allergic signs and symptoms, such as anaphylaxis. May assist in diagnosing and monitoring mast cell activation disorders or in evaluating histamine production over a longer time frame. A 24-hour urine collection of 300 mL or greater is required. If submitting a random urine or 24-hour collection with a total volume of less than 300 mL, refer to N-Methylhistamine, Random Urine (3002743).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.


24-hour urine.

Specimen Preparation

From a well-mixed 24-hour collection transfer 5 mL urine to an ARUP standard transport tube. (Min: 3 mL)
Test is not performed at ARUP; separate specimens must be submitted when multiple tests are ordered.

Storage/Transport Temperature

Refrigerated. Also acceptable: Room temperature or frozen.

Unacceptable Conditions

Collection duration and urine volume must be provided for testing. Total collection volume must be greater than 300 mL.


Ambient: 2 weeks; Refrigerated: 28 days; Frozen: 28 days


Quantitative Liquid Chromatography-Tandem Mass Spectrometry/Colorimetry




3-10 days

Reference Interval

By Report

Interpretive Data

Compliance Category

Performed by non-ARUP Laboratory


Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
2011035 Collection Duration 13362-9
2011036 Urine Volume 3167-4
2011037 N-Methylhistamine, 24 Hr Urine 44340-8
2011038 Creatinine Concentration, 24 Hr Urine 20624-3
3002790 Creatinine, 24 Hr Urine 2162-6
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • 1-Methylhistamine
  • Histamine Metabolites
  • Urinary N-Methylhistamine
N-Methylhistamine, 24-Hour Urine

Mayo Clinic Laboratories