N-Methylhistamine, 24-Hour Urine

Test Codes

Order Reference Lab Miscellaneous Send Out: EPIC: LAB848, Beaker: Ref Lab Misc., MAYO: NMH24

Department

Send Outs

Instructions

• Please refer to the Specimen Collection Manual for instructions on 24-Hour Urine Collection:
• Urine 24-Hour Collection - Inpatient
• Urine 24-Hour Collection - Outpatient
• Urine 24-Hour Collection - Outreach

Specimen Collection Criteria

Collect (preferred specimen): 24-hour urine sample with no preservative. Keep 24-hour urine specimen iced or refrigerated during collection.

• Include start and end dates and times for the collection period on the specimen container.

Urine Preservative Options
No Preservative	6N Hydrochloric Acid	Boric Acid (10g)	Sodium Carbonate	50% Acetic Acid
REQUIRED	Acceptable	Acceptable	Acceptable	Acceptable

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Entire 24-hour urine collection refrigerated (2-8°C or 36-46°F).

Rejection Criteria

Specimens not collected and processed as indicated. 

In-Lab Processing

Measure total volume of 24-hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot 5.0 mL from the well-mixed 24-hour urine collection. (Minimum: 1.75 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 14 days
Refrigerated (2-8°C or 36-46°F): 28 days
Frozen (-20°C/-4°F or below): 28 days

Specimen Storage in Department Prior to Disposal: 14 days

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN.

Performed

Monday, Wednesday, Friday.
Results available in 3-7 days.

Reference Range

By report.

Test Methodology

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Enzymatic Colorimetric Assay.

CPT Codes

82542

Contacts

Last Updated

3/23/2026