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Serum Magnesium 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. It helps assess whether your magnesium levels are within a healthy range.

Quick summary

["Magnesium levels can affect muscle and nerve function, heart health, and overall well-being."]

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

Key facts at a glance

LOINC
9478-9
Short code
Magnesium Wat-mCnc
Synonyms
Magnesium Wat-mCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
1.7
Ref high
2.2
Critical range
1 N/A – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83735
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 magnesium test to diagnose or monitor conditions such as low or high magnesium levels, muscle cramps, seizures, irregular heartbeat, or certain heart conditions. It can also be used to check for electrolyte imbalances or to evaluate symptoms like nausea, weakness, or numbness.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it is analyzed to determine the magnesium concentration. No special preparation is typically needed, but you may be asked to avoid certain medications or foods for a short time before the test.

What Are Common Symptoms?

Symptoms of low magnesium can include muscle twitches, spasms, cramps, or weakness. High magnesium levels are less common and may cause symptoms like nausea, vomiting, or irregular heartbeat. Some people may not show symptoms at all.

What Do Results Mean?

Results are compared to a reference range provided by your healthcare provider. If your results fall outside this range, further evaluation may be needed to determine the cause and appropriate treatment.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Magnesium Level

Frequently asked questions

What causes low magnesium levels?
Low magnesium levels can result from poor diet (low intake of foods rich in magnesium), certain medications, chronic kidney disease, excessive sweating, or conditions like alcoholism.
What causes high magnesium levels?
High magnesium levels are less common and can be caused by kidney problems that don’t remove enough magnesium from the body, certain medications, or severe dehydration.
Can magnesium levels change over time?
Yes, magnesium levels can fluctuate due to diet, hydration status, medications, and underlying health conditions. Regular monitoring may be necessary for people with chronic conditions or those taking medications that affect magnesium.
  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