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Magnesium, Urine

Urine Magnesium

Test Codes

24-Hour Urine: EPIC: LAB6601, Beaker: MAG24, Random Urine: EPIC: LAB5088, Beaker: MAGU

Department

Chemistry

Instructions

Note: 24-hour and random urine specimens MUST be collected separately. See below for collection criteria.

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

Specimen Collection Criteria

Collect: 24-hour urine or timed urine specimen with a 24-hour urine container with 15.0 mL of 6N Hydrochloric Acid added prior to the start of collection.
Also acceptable: Random urine specimen in a screw-capped container (preferred) or another sterile collection cup with no preservative. (Minimum: 30.0 mL) 

• Refer to the table of Urine Preservative Options when multiple tests are requested.
• 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
Acceptable	Preferred	Acceptable	Unacceptable	Unacceptable

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, or random urine, 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 a minimum of 10.0 mL from the well-mixed 24-hour urine collection.

Storage

Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): For longer storage.

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days (Royal Oak and Troy store an aliquot for 30 days.)

Laboratory

Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory

Performed

Sunday – Saturday.
Results available within 24 hours.

Reference Range

Urine Magnesium: 50-200 mg/24 hours.
Normal ranges for random urines or for collections other than 24 hours have not been established.

Test Methodology

Spectrophotometry.

Interpretation

• Low urinary magnesium levels are associated with magnesium deficiency.
• Increased levels may be due to alcohol consumption, diuretics, corticosteroids, cisplatin therapy, and Bartter's syndrome.

Clinical Utility

Magnesium measurements aid in the diagnosis and management of hypomagnesemia (abnormally low plasma levels of magnesium) and hypermagnesemia (abnormally high plasma levels of magnesium). Urine magnesium is measured as part of the Stone Former Panel and is useful in assessing the likelihood of stone formation.

CPT Codes

83735

Contacts

Last Updated

11/11/2023