Skip to content

Magnesium, Serum 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 serum.

Quick summary

["Your magnesium level helps doctors check for deficiencies or excesses that could affect your health."]

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

Key facts at a glance

LOINC
29912-3
Short code
Magnesium Stl-mRate
Synonyms
Magnesium Stl-mRate
Category
electrolyte
Sample
stool
Container
Clean 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
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors may order this test if you have symptoms like muscle weakness, cramps, irregular heartbeat, or signs of electrolyte imbalances. It’s also used to monitor conditions like hypomagnesemia (low magnesium) or hypermagnesemia (high magnesium), especially in people with kidney problems or certain medications.

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 you’re taking, as some can affect results.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a slight pinch, but it’s over quickly. The blood sample is sent to a lab for analysis.

What the Results Mean

Results are compared to standard reference ranges, but your doctor will interpret them in the context of your overall health and symptoms. Very low or very high levels can signal underlying health concerns.

Reference range

Adult: 1.7-2.2 mg/dLN/A

Specimen: stool

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low magnesium levels can disrupt nerve and muscle function, weaken the immune system, and increase the risk of heart rhythm problems. High levels may cause nausea, confusion, or slowed heart rate. Chronic imbalances can worsen conditions like diabetes, hypertension, or kidney disease.

Short name

Magnesium Level

Frequently asked questions

What causes low magnesium levels?
Low magnesium can result from poor diet (low intake of foods like nuts, leafy greens, or whole grains), kidney problems, vomiting/diarrhea, or certain medications (e.g., diuretics, antibiotics).
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you once they’re ready.
Can I eat or drink before the test?
If fasting is required, avoid food and liquids (except water) for 8–12 hours before the test. If no fasting is needed, eat and drink normally, but check with your provider for specifics.
  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