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Serum or plasma concentration of magnesium (mass concentration)

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

This test measures the amount of magnesium in your blood, which helps your muscles and nerves work properly.

Quick summary

["Magnesium helps with muscle and nerve function; low or high levels may indicate health concerns."]

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

Key facts at a glance

LOINC
82842-6
Short code
LKM IgG Ser Ql IF
Synonyms
LKM IgG Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 this test to check for magnesium deficiency or excess, especially if you have symptoms like muscle weakness, cramps, irregular heartbeat, or conditions like kidney disease, diabetes, or certain medications affecting magnesium levels.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s a fasting sample, but confirm with your lab. Avoid taking magnesium supplements or certain medications for 24 hours before testing.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but it’s quick and painless. The blood is sent to a lab for analysis.

What Does the Test Result Mean?

Results are compared to a standard range for healthy adults. Low magnesium may suggest conditions like malnutrition, diarrhea, or kidney problems, while very high levels could indicate overuse of supplements or certain medical treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Magnesium Level

Frequently asked questions

How long does it take to get my test results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Follow-up with your doctor to discuss findings and next steps.
Can I eat or drink before this test?
If fasting is required, avoid food and liquids (except water) for 8–12 hours before drawing blood. If not fasting, eat a normal meal. Always confirm instructions with your lab or doctor.
What if I’m on magnesium supplements?
Stop taking magnesium supplements or certain medications (e.g., antacids with magnesium) for 24 hours before testing to avoid interfering with results. Ask your doctor or pharmacist for guidance.
  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