Test library
Magnesium Urine Excretion Test
The Magnesium Urine Test measures magnesium excreted in urine, which helps evaluate how the kidneys handle magnesium and supports the assessment of low or high magnesium levels.
Order Magnesium, Urine Test
Order online and visit a local collection site, or choose an at-home kit where available. No referral and no insurance required.
Order Magnesium, Urine Test- Typical turnaround
- 1-3 business days
- Starting price
- From $152
- Results
- Confidential, online
Quick answer
The Magnesium Urine Test measures how much magnesium leaves the body through urine. Because the kidneys are the main regulators of magnesium balance, a urine measurement adds information that a blood level alone cannot provide. It is often ordered together with a serum magnesium test, and sometimes with a timed collection, to see whether the kidneys are conserving or wasting magnesium.
What this test measures
The kidneys filter magnesium and then reabsorb most of it, adjusting the amount excreted to keep body levels steady. A urine magnesium measurement can therefore show whether the kidneys are holding onto magnesium appropriately or losing more than expected. It may be collected as a random sample or as a timed collection, most often over a full day.
For a timed collection, all urine produced during the collection period is saved and the total volume is measured. The laboratory reports the magnesium concentration and, when a timed collection is used, the total amount excreted. Calculating the fractional excretion of magnesium requires comparing urine and serum values along with creatinine, so paired samples are sometimes ordered.
Providers order this test when magnesium imbalance is suspected and they need to understand the kidney's role. It can help distinguish between low intake or digestive losses and kidney wasting. Results are interpreted with serum magnesium, kidney function, medicines, and the clinical picture. A qualified healthcare provider should explain what the findings mean.
- Magnesium in urine
- 24-hour urine volume when a timed collection is used
- Urine creatinine
- Serum magnesium when paired
- Serum creatinine when paired
- Fractional excretion of magnesium when calculated
- Calcium when included
- Potassium when included
Why people order this test
- Evaluate how the kidneys handle magnesium
- Investigate the cause of low magnesium levels
- Check for kidney magnesium wasting
- Support a metabolic assessment when serum results are unclear
- Follow up on abnormal magnesium findings with additional testing
How to prepare
Follow the laboratory's instructions carefully. A timed collection requires saving all urine for the full collection period and keeping it refrigerated as directed. For a random sample, a fresh specimen is collected at the laboratory.
Understanding your results
Results are typically available within one to three business days after the sample reaches the laboratory. The value is interpreted alongside serum magnesium and kidney function, and a qualified healthcare provider determines what it means for the individual.
Magnesium Urine Excretion Test by state
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Connecticut
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Delaware
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Florida
Magnesium Urine Excretion Test across Florida.
Georgia
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Frequently Asked Questions
Why measure magnesium in urine instead of blood?
Urine magnesium shows how the kidneys are handling magnesium, which adds information that a blood level alone cannot provide.
Do I need a 24-hour collection?
Some orders use a random urine sample and others use a timed collection. The instructions on your laboratory order specify which type is required.
What is fractional excretion of magnesium?
It is a calculation that compares magnesium and creatinine in urine and blood to estimate how much filtered magnesium the kidneys are excreting.
Can diet affect the result?
Recent magnesium intake can influence urine levels over the short term. Share your usual diet and any supplements with the ordering provider.
How should a timed collection be stored?
Follow the laboratory's instructions, which usually include keeping the container refrigerated during the collection period and returning it promptly.
Ready to get tested?
Order online and visit a collection site near you, or choose a mail-in kit. No referral and no insurance required.
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