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Serum Magnesium Level (Mass Concentration)

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

This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood serum.

Quick summary

["Magnesium helps with muscle and nerve function, blood pressure, and energy production."]

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

Key facts at a glance

LOINC
29911-5
Short code
Magnesium Stl-mCnc
Synonyms
Magnesium Stl-mCnc
Category
electrolyte
Sample
stool
Container
Clean container
Units
N/A
Ref low
1.7
Ref high
2.2
Critical range
1 N/A – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83735
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order a magnesium test to check for low or high levels, which can cause symptoms like muscle cramps, weakness, or irregular heartbeat. It may also be 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 usually needed, but you may be asked to fast for a few hours before the test if it’s part of a broader blood panel. Bring any medications you’re currently taking to your appointment.

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 quick pinch, but it’s usually over quickly. The blood sample is then sent to a lab for analysis.

What Do Results Mean?

Results help doctors determine if your magnesium levels are within the normal range or if further action is needed. Low magnesium can lead to muscle spasms or heart issues, while very high levels may cause nausea or irregular heartbeat.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: stool

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Magnesium (Serum)

Frequently asked questions

What Are Common Causes of Abnormal Results?
Low magnesium levels can occur due to poor diet, kidney problems, vomiting, diarrhea, or certain medications. High levels may result from overuse of magnesium supplements, kidney disease, or certain medical conditions like Addison’s disease.
How Long Does It Take to Get Results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
Can I Eat or Drink Before the Test?
If fasting is required, follow your doctor’s instructions. Otherwise, you can eat and drink normally unless specified otherwise.
  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