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Magnesium, Serum

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

["Magnesium helps with muscle and nerve function, energy production, and bone health."]

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

Key facts at a glance

LOINC
23277-7
Short code
M gallisep Ag Spec Ql ImStn
Synonyms
M gallisep Ag Spec Ql ImStn
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
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 Might This Test Be Ordered?

Your doctor may order a serum magnesium test to check for low or high levels, which can affect heart rhythm, muscle function, or other health conditions. It might be done if you have symptoms like muscle weakness, cramps, or irregular heartbeat, or if you’re taking certain medications that affect magnesium levels.

What to Expect Before the Test

No special preparation is usually needed, but your doctor might advise avoiding certain foods or supplements (like antacids or laxatives) that can temporarily alter magnesium levels. Drink plenty of water the day of the test.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The blood sample will be sent to a lab for analysis. The test typically takes a few minutes, and you can return to normal activities afterward.

What Are Common Results?

Results are compared to standard reference ranges, but exact values can vary by lab. Low magnesium (hypomagnesemia) or high magnesium (hypermagnesemia) may signal underlying health concerns.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Magnesium Levels Matter

Short name

Serum Magnesium

Frequently asked questions

What Causes Low or High Magnesium Levels?
Low magnesium can result from poor diet, certain medications, kidney problems, or conditions like diabetes. High magnesium levels are less common but may occur with kidney failure, excessive supplements, or certain medical treatments.
How Might My Doctor Use This Test?
Your doctor may use the results to diagnose conditions like muscle spasms, heart arrhythmias, or metabolic disorders. It can also help monitor treatment for conditions like hypomagnesemia or hypermagnesemia.
Will I Need Follow-Up Tests?
If your magnesium levels are out of the normal range, your doctor may recommend further testing or adjustments to your treatment plan, depending on your symptoms and overall health.
  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