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Magnesium and Creatinine, Urine/Stool

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

Measures magnesium and creatinine in a urine or stool sample to help assess magnesium levels, kidney excretion, or digestive losses.

Quick summary

["This test can help evaluate magnesium balance, but results must be interpreted with the specimen type and collection instructions provided by your clinician."]

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

Key facts at a glance

LOINC
33950-7
Short code
Magnesium/Creat Ur-sRto
Synonyms
Magnesium/Creat 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 and creatinine in the specimen requested by your clinician. Magnesium is an essential mineral, while creatinine is a waste product that can help laboratories account for urine concentration or compare measurements with other values.

Why might I need this test?

Urine testing may be used to evaluate how much magnesium the kidneys are excreting, particularly when magnesium supplements or certain medicines are involved. Stool testing may help assess digestive losses of magnesium when symptoms suggest malabsorption or an unbalanced diet.

How is the test performed?

A laboratory analyzes a urine or stool sample you provide. Your clinician will determine which specimen is needed and may request a single collection, a timed collection, or a 24-hour urine collection.

How do I prepare for the test?

Follow the specific collection instructions from your clinician or laboratory. If timed or 24-hour urine collection is required, record all urine during the stated period and store it as directed; for stool testing, collect the designated amount in the provided clean container.

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/Stool Magnesium and Creatinine

Frequently asked questions

Does this test require a blood sample?
No. Despite the abbreviation used in laboratory systems, this test is performed on urine or stool, depending on the order.
Why is creatinine measured with magnesium?
Creatinine can provide context about urine concentration and may be used to calculate or compare results. A stool creatinine result may be used differently by the laboratory.
Should I change my diet or supplement use before testing?
Do not change your diet or medicines unless your clinician tells you to. If you take magnesium supplements, mention the product and timing because they can affect the result.
  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