Quick Facts
- Sample: 24-hour urine collection
- Fasting: No fasting required
- Turn-around: 2-3 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Get deeper insights than blood tests alone reveal about magnesium balance
- Identify root causes of abnormal magnesium levels and electrolyte imbalances
- Monitor kidney function and detect potential magnesium wasting disorders
- Assess supplement effectiveness and optimize your nutritional status
- Prevent complications from undiagnosed magnesium deficiency or excess
- No doctor visit required for convenient direct-access health monitoring
Who Is This Test For?
- Individuals experiencing muscle cramps, weakness, or heart rhythm irregularities
- People with diabetes (32% have magnesium deficiency) (International Journal of Endocrinology, 2023)
- Those taking medications affecting magnesium levels (diuretics, antibiotics, PPIs)
- Patients with kidney stones or chronic kidney disease
- Individuals with gastrointestinal disorders affecting nutrient absorption
- People monitoring magnesium supplementation or concerned about toxicity
How It Works – Just 3 Steps
- Order online and receive your collection kit with detailed instructions
- Collect all urine for 24 hours in the provided container, keeping refrigerated
- Return to lab and get results within 2-3 business days via secure online portal
FAQ
What does this test measure? This test measures the total amount of magnesium your kidneys excrete over 24 hours, helping evaluate magnesium balance and kidney function.
How is this different from a blood magnesium test? While blood tests show current magnesium levels, urine testing reveals how your body processes and eliminates magnesium, providing insights into the underlying cause of imbalances.
What if I miss some urine during collection? Missing urine can affect accuracy. If you forget a collection, note the time gap and inform the lab, as they may recommend restarting the test.
Can medications affect my results? Yes, diuretics, some antibiotics, and proton pump inhibitors can influence magnesium excretion. List all medications on your test form.
What happens if my results are abnormal? Abnormal results may indicate kidney problems, nutritional deficiency, or medication effects. Consult a healthcare provider for interpretation and next steps.
Is the collection process sanitary and safe? Yes, the provided collection container is sterile, and proper refrigeration during collection maintains sample integrity safely.
More Details
What is the purpose of this test?
The Magnesium 24-Hour Urine Test measures magnesium excretion to help diagnose the cause of abnormal serum magnesium levels, evaluate kidney function, and assess nutritional adequacy (Mayo Clinic Laboratories, 2025). This test uses atomic absorption spectrometry or colorimetric methods to provide quantitative results that help clinicians determine if magnesium imbalances stem from dietary insufficiency, absorption problems, or kidney dysfunction.
The test also helps calculate fractional excretion of magnesium, a key indicator of renal magnesium wasting, and assists in evaluating kidney stone risk since magnesium inhibits calcium crystal growth.
Who would benefit from this test?
This test is particularly valuable for individuals with Type 2 diabetes, where magnesium deficiency affects 32% of patients globally (International Journal of Endocrinology, 2023). People experiencing symptoms like muscle weakness, irregular heartbeats, or unexplained fatigue should consider testing, as these may indicate magnesium imbalance.
Patients taking medications known to affect magnesium levels—including diuretics, certain antibiotics, and proton pump inhibitors—benefit from regular monitoring. Those with gastrointestinal disorders affecting nutrient absorption, kidney disease, or individuals at risk for cardiovascular events also find this test valuable for comprehensive health assessment.
When should I order this test?
Consider ordering when experiencing symptoms of magnesium deficiency such as muscle cramps, weakness, or abnormal heart rhythms. The test is also useful if you have diabetes, kidney disease, gastrointestinal disorders, or take medications affecting magnesium levels.
Recent research shows hypomagnesemia increases ischemic stroke risk with adjusted odds ratios of 8.11 for patients over 65 (Journal of Neurocritical Care, 2022), making early detection crucial. Order this test for monitoring kidney stone risk, evaluating unexplained electrolyte abnormalities, or assessing the effectiveness of magnesium supplementation.
How do I interpret the results?
Understanding your results requires evaluating them alongside symptoms and other health factors. Here's a general interpretation guide:
>24 mg/day with low blood Mg
- What it means: Kidney magnesium wasting
- Typical action: Evaluate kidney function, medication review
<24 mg/day with low blood Mg
- What it means: Inadequate intake or GI losses
- Typical action: Assess diet, absorption, supplement needs
<2.4 mmol/24hr
- What it means: Reduced kidney function or low intake
- Typical action: Further kidney testing, dietary evaluation
>6.5 mmol/24hr
- What it means: Possible hyperaldosteronism or medication effect
- Typical action: Medical evaluation, medication review
Normal range (varies by lab)
- What it means: Adequate magnesium balance
- Typical action: Continue current approach
Normal individuals excrete >70% of magnesium loading doses within 24 hours, while deficient individuals retain significant amounts (Royal Liverpool University Hospital, 2024).
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.
Pre-test preparation
No special dietary restrictions are typically required, but inform your healthcare provider about all medications, supplements, and herbal products you're taking. Certain medications affecting magnesium levels may need temporary discontinuation if medically appropriate.
Obtain the proper collection container from the laboratory before beginning collection. Plan to be home or have consistent access to the collection container throughout the 24-hour period, as missing collections can significantly affect accuracy.
How often should I get tested?
Testing frequency depends on your health status and risk factors:
- Healthy individuals: Every 2–3 years or as needed
- Diabetes management: Every 6–12 months
- Kidney disease monitoring: Every 3–6 months
- Medication effects (diuretics, PPIs): Every 6 months
- Magnesium supplementation: 1–3 months after starting, then annually
- Gastrointestinal disorders: Every 6–12 months
Why early detection matters
Magnesium deficiency affects multiple body systems and often goes undiagnosed. Research shows that long-term nonprescription magnesium supplement use reduces heart failure risk (HR 0.94) and major adverse cardiac events, with stronger effects in patients with low serum magnesium levels (American Heart Association Journal, 2025).
Early detection prevents complications including cardiovascular disease, bone disorders, and neurological symptoms. Since magnesium functions as a cofactor in over 300 enzymatic reactions, maintaining optimal levels supports energy production, protein synthesis, and immune function.
Related tests you may consider
Magnesium Serum Test to measure the level of magnesium in the blood.
Comprehensive Metabolic Panel (CMP-14) with eGFR Blood Test is commonly used to evaluate nutrient levels, liver, and kidney function.
Calcium Urine Test, 24-Hour, measures calcium levels in the urine over 24 hours to help screen for, diagnose, and monitor various conditions related to the bones, heart, nerves, kidneys, and teeth.
