Skip to content

Magnesium, Serum or Plasma 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.

Quick summary

["Magnesium helps with muscle and nerve function, bone health, and energy production."]

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

Key facts at a glance

LOINC
27122-1
Short code
Magnesium RBC-mCnt
Synonyms
Magnesium RBC-mCnt
Category
electrolyte
Sample
whole-blood
Container
Lavender-top (EDTA)
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
SNOMED
900000000000003001
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for low or high magnesium levels, which can affect muscle weakness, heart rhythm, or other health issues. It may also be done if you have symptoms like cramps, spasms, or irregular heartbeat.

What to Expect Before the Test

No special preparation is usually needed, but you might be asked to fast for a few hours before the blood draw if your test is part of a metabolic panel. Bring any medications you’re taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it’s usually over quickly. The blood is sent to a lab for analysis.

What Are Common Results?

Results are reported as a mass concentration (typically in milligrams per deciliter, mg/dL). Your provider will interpret the results in relation to your overall health and symptoms.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

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 (low intake of foods like nuts, leafy greens, or whole grains), certain medications, kidney problems, or excessive sweating.
How is magnesium treated?
Treatment depends on the cause. If diet or supplements aren’t enough, your provider may recommend oral or intravenous magnesium supplements.
Can magnesium levels change with diet?
Yes, foods rich in magnesium (like spinach, almonds, or avocados) can help maintain healthy levels. However, diet alone may not correct severe imbalances.
  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