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Magnesium, Serum Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood serum.

Quick summary

["Helps assess magnesium levels, which are important for muscle and nerve function, bone health, and energy production."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
31901-2
Short code
M gallisep Ag Spec Ql
Synonyms
M gallisep Ag Spec Ql
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 this test to check for low or high magnesium levels, which can cause symptoms like muscle cramps, weakness, irregular heartbeat, or numbness. It’s often used when you have symptoms of magnesium deficiency or when other tests suggest an imbalance.

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 is part of a broader metabolic panel. Wear a loose shirt for easy access.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a slight pinch, but it’s over quickly. The blood sample is then sent to a lab for analysis.

What Are the Possible Results?

Results will show your magnesium level compared to what’s considered normal for your body. While reference ranges can vary slightly by lab, low levels may indicate conditions like malnutrition, kidney problems, or certain medications affecting absorption.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Magnesium is crucial for muscle and nerve function, blood pressure regulation, and maintaining healthy bones. Low magnesium levels can lead to muscle spasms, heart rhythm issues, or weakened immunity, while high levels may cause nausea, irregular heartbeat, or confusion. Your provider will interpret results in the context of your overall health and symptoms.

Short name

Serum Magnesium

Frequently asked questions

What causes low magnesium levels?
Low magnesium can result from poor diet (low intake of foods like nuts, leafy greens, or whole grains), kidney problems that don’t properly remove excess magnesium, vomiting or diarrhea, or certain medications (e.g., diuretics). Chronic alcohol use can also deplete magnesium levels.
What causes high magnesium levels?
High magnesium levels are less common but can occur with kidney failure (which can’t remove excess magnesium), overuse of magnesium supplements or antacids, or certain medical conditions like Addison’s disease. Rarely, it may be hereditary.
How often should I get this test?
Your provider will determine how often you need this test based on your health status, symptoms, or other conditions. Regular monitoring may be needed if you have chronic kidney disease, heart conditions, or take medications that affect magnesium levels.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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