Magnesium/Creatinine Ratio, 24-Hour Urine
Measures the ratio of magnesium to creatinine in urine collected over 24 hours to help assess how the kidneys handle magnesium.
["This test helps evaluate magnesium excretion and can identify unusually low or high urinary magnesium levels."]
Key facts at a glance
- LOINC
- 50873-9
- Short code
- Magnesium/Creat 24h Ur-sRto
- Synonyms
- Magnesium/Creat 24h Ur-sRto
- Category
- kidney
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 1.7
- Ref high
- 2.2
- Critical range
- 1 N/A – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 83735
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test measures magnesium relative to creatinine in a 24-hour urine collection. The ratio helps account for differences in urine concentration and provides information about how much magnesium the kidneys are excreting.
Why might I need this test?
It may be used to evaluate low or high magnesium levels, investigate symptoms related to magnesium imbalance, or assess kidney handling of magnesium. Results may also be interpreted alongside blood magnesium tests, kidney function, medications, and dietary intake.
How is the test performed?
You collect all urine for 24 hours in the container provided by the laboratory. The laboratory measures magnesium and creatinine in the collected urine and calculates their ratio.
How do I prepare for the test?
Follow the laboratory's urine-collection instructions carefully and note the collection start and end times. Tell your clinician if you take magnesium supplements, other medicines, or diuretics, because these can affect the results.
Reference range
Adult: 1.7-2.2 mg/dLN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A low ratio may reflect reduced magnesium intake or body stores, increased kidney loss, or effects of certain medicines. A high ratio may occur with increased magnesium intake or supplementation, reduced kidney function, or conditions that alter magnesium handling. The result should be interpreted with other laboratory findings and your clinical history.
Short name
24-Hour Urine Magnesium/Creatinine Ratio
Frequently asked questions
Why is a 24-hour urine collection needed?
Does this test show whether I have too much magnesium?
Can magnesium supplements affect the result?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy