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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

["Your blood magnesium levels help assess overall mineral balance and potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
17310-4
Short code
MAG Ab Ser Ql IF
Synonyms
MAG Ab Ser Ql IF
Category
glucose
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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?

Doctors 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 used in cases of symptoms like muscle weakness, cramps, irregular heartbeat, or conditions like kidney disease, diabetes, or certain medications affecting magnesium.

What to Expect Before the Test

You’ll typically have a small needle inserted into your arm to draw blood. No special preparation is needed, but inform your provider about any medications or supplements you take, as they may influence results.

What the Results Mean

While reference ranges vary by lab, low magnesium can cause muscle spasms, numbness, or heart rhythm issues, while very high levels may lead to nausea, confusion, or irregular heartbeat. Your doctor will interpret results in the context of your overall health.

Common Conditions Linked to Magnesium Levels

Serum magnesium tests are commonly checked in patients with symptoms of magnesium deficiency (e.g., fatigue, irregular heartbeat) or those at risk due to conditions like chronic kidney disease, malnutrition, or certain medications (e.g., diuretics, antacids).

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum Magnesium

Frequently asked questions

What causes my magnesium levels to be abnormal?
Abnormal magnesium levels can result from dietary deficiencies, kidney problems (which may fail to excrete excess magnesium), certain medications, or metabolic disorders. Chronic conditions like diabetes or heart disease may also influence results.
How long will it take to get my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you once they’re ready for review.
Can I eat or drink before this test?
You can eat and drink normally before the test, as fasting isn’t required. However, avoid alcohol or caffeine in excess, as they may temporarily 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