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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 levels help assess your body’s mineral balance and overall health."]

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

Key facts at a glance

LOINC
108964-8
Short code
MAG IgG Msmt Ser
Synonyms
MAG IgG Msmt Ser
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 this test to check for low or high magnesium levels, which can affect muscle function, nerve signals, and heart health. It may also be used to monitor 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 blood draw if your test involves fasting-related interpretation. Wear a loose-fitting shirt for easy access.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it typically only takes a few minutes. The blood sample will be sent to a lab for analysis.

What Are Possible Results?

Results are interpreted by your healthcare provider based on your overall health, symptoms, and medical history. Abnormal results may indicate deficiencies or excesses that require further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Magnesium

Frequently asked questions

How long does it take to get my results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will contact you once they have the results and discuss them with you.
Can I eat or drink anything before the blood test?
If fasting is required for your test, avoid food and liquids (except water) for at least 8–12 hours before drawing blood. Follow your provider’s instructions to ensure accurate results.
What are common causes of low or high magnesium levels?
Low magnesium levels may result from poor diet, kidney problems, vomiting, diarrhea, or certain medications. High magnesium levels can occur due to kidney failure, excessive supplements, or certain medical conditions like Addison’s disease. Your provider will evaluate these factors along with your test results.
  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