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Serum or Plasma Magnesium Concentration (Qualitative or Quantitative)

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

This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood. Low or high levels may indicate health concerns.

Quick summary

["Magnesium levels help assess electrolyte balance and potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
31511-9
Short code
M gallisep Ab Ser-aCnc
Synonyms
M gallisep Ab Ser-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like muscle weakness, cramps, irregular heartbeat, or signs of electrolyte imbalances. It could also be part of routine check-ups, especially if you have conditions like kidney disease, diabetes, or heart problems.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast before the test, but this depends on the lab’s instructions. Avoid excessive alcohol or certain medications that could affect results.

During the Test

A small needle will be inserted into your arm to draw blood. You may feel a slight pinch, but it only takes a few minutes. The blood sample is then sent to the lab for analysis.

What the Results Mean

Results are typically reported as a concentration (e.g., milligrams per deciliter). While reference ranges vary by lab, low levels may suggest magnesium deficiency, while high levels could indicate overabsorption or kidney issues.

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 like nuts, leafy greens, or whole grains), certain medications (e.g., diuretics, antacids), kidney problems, or chronic conditions like diabetes.
What causes high magnesium levels?
High magnesium levels may occur due to kidney failure (which can’t remove excess magnesium), excessive intake of magnesium supplements, or rare genetic disorders. Severe cases can lead to dangerous heart rhythms.
How often should I get this test?
Your provider will determine frequency based on your health status. Routine adults may not need this test unless they have risk factors, while those with chronic conditions may need monitoring more often.
  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