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Magnesium, Ionized, Serum

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

This test measures the amount of magnesium that is electrically charged (ionized) in your blood serum. Ionized magnesium is the active form of magnesium that helps regulate important bodily functions.

Quick summary

["Ionized magnesium levels can indicate how well your body is balancing minerals and supporting nerve and muscle function."]

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

Key facts at a glance

LOINC
32698-3
Short code
Mg Ionized SerPl-mCnc
Synonyms
Mg Ionized SerPl-mCnc
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 is this test done?

Your doctor may order this test if you have symptoms like muscle weakness, cramps, or irregular heartbeat. It can also help diagnose conditions such as low or high magnesium levels, kidney problems, or metabolic disorders.

What does the test involve?

A blood sample is taken from a vein, usually in your arm. The blood is then processed to separate the serum, which is analyzed for ionized magnesium levels using specialized laboratory techniques.

What might affect results?

Several factors can influence magnesium levels, including diet (e.g., foods rich in magnesium like nuts, leafy greens), certain medications, kidney function, and dehydration. Recent exercise or stress can also temporarily affect results.

Preparation for the test

No special preparation is usually needed, but you may be asked to fast for a few hours before the test if instructed by your healthcare provider. Avoiding certain medications or supplements for a day or two beforehand can sometimes improve accuracy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low ionized magnesium levels can cause muscle spasms, weakness, or irregular heart rhythms. High levels may lead to symptoms like nausea, vomiting, or confusion. Chronic imbalances can affect heart health, nerve function, and overall metabolism. This test helps monitor conditions like hypomagnesemia, hypermagnesemia, or electrolyte imbalances.

Short name

Ionized Magnesium

Frequently asked questions

How long does it take to get results?
Results are typically available within one to three business days, depending on your lab’s processing time.
Can I eat or drink before the test?
You may eat and drink normally unless your doctor specifies otherwise. Some tests require fasting, but this test does not.
What if my results are outside the normal range?
If your results are outside the normal range, your doctor will discuss them with you and may recommend further testing or adjustments to your treatment plan, such as dietary changes or medication adjustments.
  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