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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, blood pressure, and bone health."]

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

Key facts at a glance

LOINC
54919-6
Short code
Magnesium Smn-mCnc
Synonyms
Magnesium Smn-mCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
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 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 Might You Need This Test?

Your healthcare provider may order this test if you have symptoms like muscle weakness, cramps, irregular heartbeat, or signs of electrolyte imbalances. It can also be part of routine checks for conditions like kidney disease, diabetes, or heart problems.

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’s part of a metabolic panel. Bring any medications or supplements you’re taking, as they can affect results.

How the Test Works

A small blood sample is drawn from a vein, typically in your arm. The sample is sent to a lab where it’s analyzed to measure magnesium levels using a specialized method, often automated and precise.

What the Results Mean

Results are compared to a reference range specific to your lab, which accounts for factors like age, sex, and overall health. Low or high levels may signal underlying health concerns that need further evaluation.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: serum

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

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. Your healthcare provider will discuss them with you during your follow-up visit.
Can I take supplements or medications before the test?
Some magnesium-containing supplements or certain medications (like antibiotics or diuretics) can affect results. Always inform your provider about all medications or supplements you’re taking before the test.
What if my magnesium level is outside the normal range?
If your results are low, your provider may recommend dietary changes, supplements, or further testing to identify the cause. If high, they might investigate conditions like kidney disease or overuse of certain medications. Follow-up may include monitoring symptoms or additional bloodwork.
  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