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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
108965-5
Short code
MAG/SGPG IgM Msmt Ser
Synonyms
MAG/SGPG IgM 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 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 also be used to monitor treatment for conditions like kidney disease, diabetes, or certain medications that affect magnesium balance.

What Does the Result Mean?

Results can vary based on your health status, diet, and other factors. Low magnesium may cause muscle cramps, weakness, or irregular heartbeat, while high levels might lead to nausea, muscle spasms, or abnormal heart rhythms. Your doctor will interpret the result in the context of your overall health.

Common Reasons for Testing

Tests for magnesium are often performed if you have symptoms like muscle twitching, seizures, or irregular heartbeat. It may also be checked during pregnancy, with kidney disease, or if you’re taking certain medications like diuretics or antibiotics that can affect magnesium levels.

How Is the Test Done?

A blood sample is taken from a vein in your arm. You may feel a small pinch, but it usually doesn’t cause discomfort. The sample is sent to a lab for analysis, and results are typically ready within 24 hours.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum Magnesium

Frequently asked questions

What Are Possible Causes of Low Magnesium?
Low magnesium (hypomagnesemia) can result from poor diet (low intake of foods like nuts, leafy greens, or whole grains), certain medications, chronic vomiting or diarrhea, kidney disease, or alcoholism. It may also be inherited or caused by conditions like diabetes or pancreatitis.
What Are Possible Causes of High Magnesium?
High magnesium (hypermagnesemia) is less common and can occur with kidney problems (which reduce excretion), excessive intake of magnesium supplements, or certain medications like laxatives or antacids. Rarely, it may be genetic or linked to adrenal insufficiency.
How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your health history, symptoms, and treatment plan. Regular monitoring may be needed if you have chronic conditions like kidney disease or are on long-term medications affecting 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