Serum or plasma concentration of magnesium (mass concentration)
This test measures the amount of magnesium in your blood, which helps maintain nerve and muscle function, support bone health, and regulate muscle contractions.
["Magnesium helps your body’s nerves and muscles work properly and keeps your bones strong."]
Key facts at a glance
- LOINC
- 35974-5
- Short code
- MRA LE ves-Bl
- Synonyms
- MRA LE ves-Bl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- mr-angio
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test to check for low or high magnesium levels, which can cause symptoms like muscle weakness, cramps, irregular heartbeat, or numbness. It may also be used to monitor conditions like kidney disease, heart problems, or certain medications that affect magnesium levels.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your test involves a specific timing (e.g., 24-hour urine). Bring any medications you’re taking to your appointment.
How the Test Is Done
A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause much discomfort. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results help doctors determine if your magnesium levels are within a healthy range. Abnormal levels can indicate underlying health issues, so follow-up may be needed if your results are outside expected limits.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Magnesium plays a critical role in many bodily functions, including muscle and nerve activity, blood pressure regulation, and bone health. Low magnesium can lead to weakness, seizures, or heart rhythm problems, while high levels may cause nausea, irregular heartbeat, or muscle spasms. Regular monitoring is important for patients with chronic conditions like diabetes, kidney disease, or those on certain medications.
Short name
Magnesium Level
Frequently asked questions
What causes low magnesium levels?
What causes high magnesium levels?
Can magnesium levels change over time?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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