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Serum or plasma concentration of magnesium

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood. It helps assess electrolyte balance and detect potential deficiencies or excesses.

Quick summary

["Magnesium levels can affect muscle function, nerve signaling, and heart health."]

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

Key facts at a glance

LOINC
23273-6
Short code
M gallisep Ab Ser Ql HA
Synonyms
M gallisep Ab Ser Ql HA
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
1.5
Ref high
9
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ha
CPT
83002
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

What Is Magnesium Used For?

Magnesium plays a key role in muscle contractions, nerve signaling, and maintaining healthy bones. It also helps regulate blood pressure and supports energy production in cells. Low levels may contribute to muscle cramps, weakness, or irregular heart rhythms, while high levels can cause nausea, muscle weakness, or irregular heartbeat.

Why Might You Need This Test?

Your doctor may order a serum magnesium test if you have symptoms like muscle spasms, weakness, irregular heartbeat, or conditions such as kidney disease, diabetes, or certain medications (like diuretics) that affect magnesium levels. It may also be checked during pregnancy or if you have a history of low magnesium.

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 significant discomfort. The sample is sent to a lab for analysis.

What Are Common Results?

Results are reported as a concentration in milligrams per deciliter (mg/dL). Your doctor will interpret the results in relation to your overall health and symptoms.

Reference range

Follicular: 1.5-9.0 mIU/mLN/A

Specimen: serum

For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.

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?
Test results typically arrive within 1 to 3 business days, depending on your lab’s processing time. Follow-up with your healthcare provider to discuss the results and next steps.
What does a low magnesium level mean?
Low magnesium levels (hypomagnesemia) may indicate conditions like malnutrition, kidney disease, or certain medications. It can also be a sign of chronic health issues like diabetes or alcohol use. Your doctor will evaluate your symptoms and other test results to determine the cause.
Can I eat or drink anything before the test?
You can eat and drink normally before the test unless instructed otherwise by your doctor. Avoid alcohol and large amounts of caffeine 24 hours before testing, as they may 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