Lab test
Magnesium Levels Blood Test - Deficiency
This blood test checks the level of magnesium in blood serum to evaluate deficiency or excess.
- Typical price
- From $28
- Results
- 1-3 business days
- Preparation
- See preparation notes below
- Sample
- Blood draw or sample collection at a local center
About this test
This blood test checks the level of magnesium in blood serum to evaluate deficiency or excess. Magnesium is a mineral involved in many biochemical reactions, including muscle and nerve function, energy production, and bone health. The test may be ordered for muscle cramps, weakness, irregular heartbeat, or when a person has a condition or takes a medicine that affects magnesium balance. Because most magnesium is stored in cells and bone, serum levels reflect only a portion of the body's total, so results are interpreted with clinical context.
What this test measures
- Magnesium (serum) Measures the amount of magnesium circulating in the blood.
Who this test may be right for
- People with muscle cramps, twitching, or weakness
- Individuals with an irregular heartbeat or palpitations
- People with conditions affecting nutrient absorption or kidney function
- Those taking medicines that can alter magnesium levels
Before your visit
- No fasting is usually required.
- Tell the collector about magnesium supplements or medicines you take.
- Follow any instructions provided for your specific panel.
Understanding your results
A low serum magnesium may suggest deficiency, which can relate to diet, absorption, or losses through the kidneys or gut. A high level may occur with excessive supplementation or impaired kidney function. Because serum magnesium does not capture all body stores, a normal result does not always rule out deficiency. Discuss results with a healthcare provider.
Order this test online
- Buy online in a few minutes - no doctor's visit needed for most tests.
- Sample collection at a patient service center near you.
- Results are typically ready within 1-3 business days.
- Secure, lab-reviewed results delivered to your account.
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Questions people ask
What is serum magnesium?
It measures the magnesium circulating in the liquid part of the blood. Because most magnesium is inside cells and bone, this test reflects only part of the body's total.
Can low magnesium cause muscle symptoms?
Magnesium helps regulate muscle and nerve function, so low levels have been associated with cramps, twitching, and weakness. A provider interprets this with other findings.
Does a normal serum magnesium rule out deficiency?
Not always. Serum levels can appear normal even when body stores are low, so a provider may order other tests if deficiency is still suspected.
Can supplements affect the test?
Yes. Recent magnesium supplements can raise serum levels, so tell the collector what you take and follow any preparation instructions.
What does the Magnesium Levels Blood Test - Deficiency measure?
This blood test checks levels of magnesium in blood serum to evaluate deficiency or toxicity.
Do I need to fast before this test?
Follow the lab's instructions.
How long do results take?
Most Magnesium Levels Blood Test - Deficiency results are released in 1-3 business days. Specialty testing can take longer.
Is this test right for me?
This page is educational and not medical advice. Talk to a licensed healthcare provider about which tests fit your situation.
LabBookings is an independent directory. We compare test details and pricing information, but we are not a laboratory and we do not perform testing or provide medical advice. Always talk to a licensed healthcare provider about your results and treatment.
Laboratory services are provided by independent, CLIA-certified testing partners. Availability, pricing, and turnaround times can vary by location and are confirmed at checkout.