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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

["Magnesium levels help assess electrolyte balance and overall health."]

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

Key facts at a glance

LOINC
23278-5
Short code
M gallisep Ag Spec Ql Nt
Synonyms
M gallisep Ag Spec Ql Nt
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
neut
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 magnesium deficiency or excess, which can affect muscle function, nerve signaling, and other vital processes. It may also be used to monitor conditions like hypomagnesemia (low magnesium), hypermagnesemia (high magnesium), or to evaluate symptoms such as muscle weakness, cramps, or irregular heartbeat.

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 instructed by your provider. Wear comfortable clothing and plan for the test to be done at a healthcare facility.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is then sent to a lab for analysis.

What Are Normal Results?

There is no specific numeric range provided here, as reference intervals can vary by lab and individual health status. Your results will be compared to your lab’s standards and discussed with your provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Magnesium

Frequently asked questions

What causes low magnesium levels?
Low magnesium levels (hypomagnesemia) can result from poor diet (low intake of foods rich in magnesium), certain medications, chronic vomiting or diarrhea, kidney problems, or excessive sweating. Lifestyle factors like heavy alcohol use may also contribute.
What are the symptoms of magnesium imbalance?
Symptoms of low magnesium may include muscle cramps, spasms, or weakness; irregular heartbeat; numbness or tingling; and fatigue. High magnesium levels may cause nausea, muscle weakness, confusion, or irregular heartbeat. Seek medical attention if you experience severe symptoms.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab and healthcare provider. Your provider will contact you once the results are ready for discussion.
  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