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Serum/plasma mass concentration of magnesium

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

This test measures the amount of magnesium in your blood. Magnesium is an essential mineral that helps with muscle and nerve function, blood pressure regulation, and bone health.

Quick summary

["Your magnesium levels help doctors check for deficiencies or excesses that could affect your health."]

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

Key facts at a glance

LOINC
38167-3
Short code
Maj XM SerPl PEG-Imp
Synonyms
Maj XM SerPl PEG-Imp
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
peg
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 if you have symptoms like muscle weakness, cramps, irregular heartbeat, or nausea. It’s also used to monitor conditions like kidney disease, heart problems, or certain medications that affect magnesium levels.

What to Expect Before the Test

No special preparation is needed, but avoid taking magnesium supplements or certain medications (like some antibiotics or diuretics) 24 hours before testing if instructed by your doctor.

What Happens During the Test?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab to measure magnesium levels using a specialized test method.

What Do Results Mean?

Results help determine if your magnesium levels are too low (hypomagnesemia) or too high (hypermagnesemia), which can impact how your body functions.

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 can result from poor diet, kidney problems, vomiting/diarrhea, certain medications, or conditions like diabetes.
What causes high magnesium levels?
High magnesium levels may occur with kidney failure, excessive magnesium supplements, or certain medications.
How often should I get this test?
Your doctor will decide based on your symptoms, medical history, and treatment needs—typically not as a routine check unless recommended.
  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