Magnesium, Serum (Mass Concentration)
This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood serum.
["Magnesium levels help assess electrolyte balance and potential deficiencies or excesses."]
Key facts at a glance
- LOINC
- 21411-4
- Short code
- MAG IgM Ser-aCnc
- Synonyms
- MAG IgM Ser-aCnc
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82784
- 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 healthcare provider may order a serum magnesium test to check for low or high levels, which can affect muscle function, nerve signals, and heart health. It’s often done if you have symptoms like muscle weakness, cramps, or irregular heartbeat, or if you have conditions like kidney disease, diabetes, 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 test if it’s part of a broader metabolic panel. Bring any medications you’re currently taking to your appointment.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a slight pinch, but it’s usually over quickly. The blood sample is then sent to a lab for analysis.
What Are Common Results?
Results are typically reported in milligrams per deciliter (mg/dL). While reference ranges can vary slightly by lab, low magnesium levels may be below 1.7 mg/dL, and high levels may exceed 2.4 mg/dL, though these are general guidelines and not absolute.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low magnesium levels (hypomagnesemia) can cause muscle spasms, tremors, irregular heartbeat, or even seizures in severe cases. High magnesium levels (hypermagnesemia) are less common but can lead to weakness, nausea, or slowed heart rate. Both conditions may require medical attention and adjustments to diet, medications, or treatments.
Short name
Serum Magnesium
Frequently asked questions
What causes low magnesium levels?
What are the symptoms of abnormal magnesium levels?
How long does it take to get results?
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