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Serum or plasma concentration of magnesium (qualitative)

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

This test checks whether your magnesium levels are too high or too low in your blood. Magnesium is an important mineral that helps with muscle and nerve function.

Quick summary

["Magnesium imbalance can affect heart rhythm, muscle function, and overall health."]

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

Key facts at a glance

LOINC
55904-7
Short code
M-IgE Ser Ql IEP
Synonyms
M-IgE Ser Ql IEP
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immunoelectrophoresis
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 Is Done

Your doctor may order this test if you have symptoms like muscle weakness, cramps, irregular heartbeat, or signs of low magnesium (such as numbness, seizures, or irregular heartbeat). It may also be done if you have conditions like kidney disease, diabetes, or certain medications that can affect magnesium levels.

What to Expect Before the Test

No special preparation is needed. You may have a blood draw from a vein in your arm, or a sample of urine may be collected if a 24-hour urine test is ordered. If you’re on certain medications, tell your healthcare provider before the test.

What the Test Results Mean

This is a qualitative test, meaning it only tells if magnesium levels are abnormal (either too high or too low), not the exact amount. Results are interpreted by your doctor based on your symptoms and medical history.

Possible Causes of Abnormal Results

Low magnesium (hypomagnesemia) can occur due to poor diet, kidney problems, vomiting, diarrhea, or certain medications. High magnesium (hypermagnesemia) is less common but can happen with kidney failure, overuse of antacids, or certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Qualitative magnesium level

Frequently asked questions

What are the normal reference ranges for magnesium in blood or urine?
This test does not provide specific numeric ranges—it only identifies whether magnesium levels are outside normal limits. Your doctor will use clinical judgment to determine if further testing or treatment is needed based on your symptoms and test results.
Can I eat or drink anything before this test?
For blood tests, you can eat and drink normally unless instructed otherwise. For a 24-hour urine test, follow your doctor’s instructions carefully—typically, you’ll collect all urine for 24 hours.
How long will it take to get my results?
Results are usually available within a few days to a week, depending on your lab and healthcare provider. Follow-up may be scheduled if your doctor needs more details.
  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