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Magnesium/Creatinine Ratio, Urine

Published: August 9, 2026Updated: August 16, 2026

A urine test that measures magnesium relative to creatinine, helping assess magnesium excretion while accounting for urine concentration.

Quick summary

["This test can help evaluate how much magnesium your body is losing in the urine."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
56956-6
Short code
Magnesium/Creat Ur-Rto
Synonyms
Magnesium/Creat Ur-Rto
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 the amount of magnesium in a urine sample and compares it with the amount of creatinine. Creatinine is used as a reference because its level in urine tends to reflect how concentrated the urine is.

Why might I need this test?

Your clinician may order this test to evaluate magnesium loss through the urine, especially if you have low blood magnesium, unexplained symptoms, kidney concerns, or a condition that may affect mineral levels.

How is the test performed?

A urine sample is collected and tested to determine its magnesium and creatinine levels. The laboratory or your clinician then uses these measurements to calculate the magnesium-to-creatinine ratio.

How do I prepare for the test?

Follow your clinician's instructions for urine collection, including whether a random or timed sample is required. Tell your clinician about magnesium supplements, other supplements, and medicines you take, but do not change your diet or treatment unless instructed.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine Magnesium/Creatinine Ratio

Frequently asked questions

Is this the same as a serum magnesium test?
No. This test measures magnesium in urine relative to creatinine, while a serum magnesium test measures magnesium in the blood.
Why is creatinine included in the result?
Urine can vary in concentration. Creatinine helps account for that variation, making the magnesium-to-creatinine ratio easier to interpret.
Do I need to stop taking magnesium supplements?
Do not stop supplements on your own. Tell your clinician what you are taking so the result can be interpreted correctly and your treatment can be adjusted if needed.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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