Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



Mg, Quantitative Urine; Magnesium, 24 hour urine

CPT Codes:

83735 – Magnesium
81050 – Volume measurement for timed collection

Test Includes:

Urine magnesium in mEq/L and mEq/collection


Test Indications:

Magnesium is an essential mineral that is found in the body and is related to other cations such as calcium, phosphate, sodium and potassium. The body maintains magnesium levels in blood, cells and bone by regulating how much it absorbs from the intestines and how much it excretes or conserves in the kidneys.

Lab Testing Sections:


Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

1 day

Special Instructions:

Submit an entire 24-hour urine collection. No preservative. Refrigerate specimen during and after collection.

Note: Starting and ending times of collection are required for a timed urine collection and must be documented electronically or on the proper request form.


Specimen Type:

Urine, timed collection


Plastic leakproof container (No preservative). Urine GUARD® collection container is preferred for a timed urine sample.

Draw Volume:

Submit an entire 24-hour urine collection

Processed Volume:

Minimum: 0.5 mL urine


For timed urine collections, empty the bladder, discard the voided sample, and note the start time. Collect all urine voided for the specified time period. At the end of the period, note the finishing time, add the last voided sample to the container by emptying the bladder. Bring the refrigerated container to the lab. Make sure all specimens submitted to the laboratory are properly labeled with the patient’s name, medical record number and date of birth.

Special Processing:

Lab Staff: The urine aliquot should be acidified before analysis to a pH of 1-2 with 6N HCL.

Patient Preparation:


Sample Rejection:

Unlabeled specimens


Reference Range:

None established

Critical Values:





Colorimetric, Methyl Thymol Blue


MG Flex® reagent cartridge insert sheet Siemens Healthcare Diagnostics, Inc (2010-02-04) PN 717057.001 US Rev L

Jacobs & DeMott Laboratory Test Handbook (2001) Lexi-Comp, Inc, Hudson, OH, 5th Edition

Biorad Liquichek Unassayed Chemistry Control Product Insert, Bio-Rad Laboratories, Irvine, CA 92618

Biorad Liquichek Urine Chemistry Control Product Insert, Bio-Rad Laboratories, Irvine, CA 92618


12/10/2013: Move from mEq/L to mg/dL. Reference range updated.

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