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Serum/plasma mass concentration of magnesium

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of magnesium in your blood, an important mineral that helps with muscle and nerve function.

Quick summary

["Magnesium levels help assess your body’s mineral balance and overall health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
1252-6
Short code
Maj XM p Imm Spin SerPl-Imp
Synonyms
Maj XM p Imm Spin SerPl-Imp
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
17
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 Is This Test Done?

Your doctor may order this test to check for low or high magnesium levels, which can cause symptoms like muscle weakness, cramps, irregular heartbeat, or other health issues. It may also be used to monitor conditions like kidney disease, heart problems, or certain medications that affect magnesium.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it involves drawing blood. Avoid taking magnesium supplements or certain medications (like some antibiotics or diuretics) for 24 hours before testing.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause discomfort. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to a standard range, but exact values can vary by lab. Low magnesium may indicate dehydration, kidney problems, or certain medical conditions, while very high levels could signal kidney disease or overuse of magnesium supplements.

Reference range

NCBI: NSE 0-17 ng/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Magnesium Level

Frequently asked questions

What causes magnesium levels to be checked?
Magnesium is essential for nerve and muscle function, blood pressure regulation, and bone health. Doctors may order this test if you have symptoms like muscle spasms, irregular heartbeat, fatigue, or if you have conditions like kidney disease, diabetes, or are taking certain medications that affect magnesium levels.
How long does it take to get results?
Test results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the results with you during your follow-up visit.
Can I eat or drink before this test?
If fasting is required (common for blood tests), avoid food and liquids—except water—for 8–12 hours before drawing blood. If no fasting is needed, you can eat and drink normally, but check with your provider for specifics.
  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 17, 2026. · Read our editorial policy