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Magnesium, Ionized (Serum)

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

This test measures the amount of magnesium in your blood that is available to be used by your body, specifically the free, ionized form which is the most biologically active.

Quick summary

["Ionized magnesium helps regulate nerve and muscle function, blood pressure, and energy production."]

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

Key facts at a glance

LOINC
2600-5
Short code
Mg Ionized SerPl-sCnc
Synonyms
Mg Ionized SerPl-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like muscle cramps, weakness, or irregular heartbeat. It could also be part of a broader evaluation for conditions like low magnesium levels (hypomagnesemia) or high levels (hypermagnesium), especially if you have kidney problems, heart issues, or certain medications affecting magnesium balance.

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 blood draw. Your provider will explain any specific instructions tailored to your situation.

How the Test Works

A small sample of your blood is taken from a vein, typically in your arm. The blood is then analyzed in a lab to measure the ionized magnesium concentration using specialized equipment that separates and quantifies the free magnesium ions.

What the Results Mean

Results are compared to a reference range specific to your age, sex, and overall health. Low levels may indicate conditions like malnutrition, kidney disease, or certain medications. High levels can be linked to kidney failure, overuse of magnesium supplements, or other health issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Ionized Magnesium

Frequently asked questions

What are the normal reference ranges for ionized magnesium?
Normal reference ranges can vary slightly between labs and individuals. Your results will be interpreted in the context of your specific health profile. Your healthcare provider will discuss any deviations from your reference range and explain their potential implications.
How long does it take to get the results of this test?
Test results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your provider will contact you once the results are ready.
Can I eat or drink anything before this test?
Most often, no special diet is required, but your provider may give specific instructions. It’s important to follow these to ensure accurate results. Always confirm with your healthcare team.
  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