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Magnesium, Serum

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

This test measures the amount of magnesium, a mineral essential for many bodily functions, in your blood serum. Low or high levels may indicate underlying health concerns.

Quick summary

["Magnesium levels help assess electrolyte balance and potential deficiencies or excesses in your body."]

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

Key facts at a glance

LOINC
30922-9
Short code
Magnesium ?Tm Ur-mCnc
Synonyms
Magnesium ?Tm Ur-mCnc
Category
electrolyte
Sample
urine
Container
Sterile urine container
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
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
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 a serum magnesium test to check for conditions like low magnesium (hypomagnesemia) or high magnesium (hypermagnesiumemia). It can also be used to monitor certain medications, kidney function, or metabolic disorders. Symptoms of imbalance may include muscle weakness, irregular heartbeat, or seizures, but tests are often done even without symptoms to prevent complications.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re taking, as some (like certain diuretics or antibiotics) may affect results. Avoid excessive alcohol or caffeine before testing, as they can influence magnesium levels temporarily.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm using a small needle. The process is quick and typically painless. You may feel a slight sting, but most people tolerate it well. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. Low magnesium may raise concerns about muscle cramps, heart rhythm issues, or long-term health risks like osteoporosis. High magnesium can signal kidney problems or overuse of magnesium supplements. Your provider will interpret results in the context of your overall health and symptoms.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Magnesium

Frequently asked questions

What causes low magnesium levels?
Low magnesium (hypomagnesemia) can result from poor diet (low intake of foods like nuts, leafy greens, or whole grains), certain medications (e.g., diuretics, antibiotics), chronic kidney disease, or malabsorption issues (e.g., celiac disease). Rarely, it may be genetic or linked to conditions like diabetes or alcohol use.
What causes high magnesium levels?
High magnesium (hypermagnesiumemia) is less common but can occur with kidney failure (since kidneys normally filter excess magnesium), overuse of magnesium supplements or laxatives, or certain medications (e.g., some antibiotics or antacids). Severe cases may require medical attention.
How often should I get this test?
Your provider will determine testing frequency based on your health status. Routine checks may be recommended if you have conditions like kidney disease, heart problems, or are taking medications that affect magnesium levels. Follow-up tests are often scheduled if initial results are outside the expected range.
  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