Quick Facts
- Sample: Urine (24-hour collection)
- Fasting: No fasting is required. Obtain a proper collection container from the lab using your lab order. Discard the first 8 AM urine, then collect all urine for the next 24 hours, ending with a final collection at 8 AM the following morning. Keep the specimen refrigerated or cool, label the container with your name and collection dates/times, and return it promptly to the lab.
- Turnaround: 2-3 business days. May take longer based on weather, holiday, or lab delays.
What This Test Measures
This test measures the amount of magnesium in your urine, collected over a full 24-hour period. Your results reflect two components: the magnesium concentration in your urine and the total volume of urine collected, which together determine the total amount of magnesium your body excreted during the collection window. This is a directly measured, quantitative result based on your urine specimen, not a blood test and not a calculated estimate from a single random sample.
Because magnesium excretion is measured over a full day rather than at one moment, this test reflects your body's magnesium handling over that specific 24-hour period rather than a single point-in-time reading.
Benefits
- Measures how much magnesium your kidneys excrete over 24 hours.
- Supports evaluation of kidney problems affecting mineral excretion.
- Helps monitor your response to oral or IV magnesium supplements.
- May support evaluation related to uncontrolled diabetes.
- Can be paired with calcium and phosphorus testing to monitor supplementation.
- Provides quantitative, lab-based results for your healthcare provider to review.
Who Is This Test For?
- Individuals being evaluated for kidney problems affecting mineral levels.
- People taking oral or IV magnesium supplements who need monitoring.
- Those undergoing calcium supplementation who need related mineral tracking.
- People whose healthcare provider is assessing magnesium status related to uncontrolled diabetes.
- Individuals being evaluated for gastrointestinal disorders affecting mineral absorption.
How It Works
- Order Your Test Online
- Visit a Local Lab
- Get Results Online
FAQ
1. What does this test measure?
This test measures the amount of magnesium in your urine, along with the total volume of urine collected, over a full 24-hour period. Together, these values determine the total amount of magnesium your body excreted during that time. Because the result comes from a directly measured urine specimen collected continuously over 24 hours, it differs from a spot urine magnesium test or a blood magnesium test, both of which capture a single point in time rather than a full day of excretion. This measurement may help your healthcare provider evaluate how your kidneys are handling magnesium and can support broader assessments related to mineral absorption or supplementation.
2. Who would benefit from this test, and when should I order it?
This test may be useful if your healthcare provider is evaluating kidney function, monitoring your response to oral or IV magnesium supplements, or assessing mineral levels alongside calcium and phosphorus testing. It may also be relevant if you're being evaluated for gastrointestinal disorders affecting mineral absorption or for uncontrolled diabetes. It works best as one part of a broader clinical picture rather than as a standalone evaluation.
3. Do I need to fast or prepare for this test?
No fasting requirement is specified for this test. Preparation instead centers on the urine collection process: you'll need a proper specimen container from your lab, and you'll discard your first morning urine before beginning the full 24-hour collection that follows.
4. How quickly will I get results?
Results are typically available in 2 to 3 days. This timeframe may extend due to weather, holidays, or other lab delays.
5. How do I interpret the results?
Your magnesium excretion result should be considered alongside factors like your kidney function, hydration status, any supplements you're taking, and the completeness and accuracy of your 24-hour collection. A result outside the expected range doesn't point to one specific cause, since multiple conditions can affect magnesium excretion.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
6. What should I do if my results are abnormal?
Share your results with a qualified healthcare provider so they can be reviewed in the context of your overall health and any related testing. Your provider may consider additional evaluation depending on your individual situation.
7. How often should I get tested?
Testing frequency depends on your individual situation and should be determined by your healthcare provider, particularly if this test is being used to monitor magnesium or calcium supplementation over time.
Pre-test preparation
You must take your lab order to the lab to obtain a proper specimen container before collection. Urinate at 8am and discard the specimen. Then collect all urine in the 24-hour period, ending with a final collection at 8am the next morning. Refrigerate the collected urine between all voidings or keep it in a cool place. Screw the lid on securely. Transport the specimen promptly to the laboratory. The container must be labeled with your full name, and the date and time the collection started and finished.
