Order Serum Magnesium Blood Test from JustLabs for $7 ($25 all-in for a single-test order: $7 + one $18 lab & physician order fee per order). Price includes lab processing at Quest Diagnostics. No insurance required.
Serum magnesium measures the level of magnesium in your blood. While useful for detecting severe deficiency, it may not reflect your true magnesium status since most magnesium is stored in cells and bones.
Magnesium is the fourth most abundant mineral in the body and is essential for over 300 enzymatic reactions, including muscle and nerve function, blood sugar control, blood pressure regulation, protein synthesis, and energy production.
This test measures magnesium in blood serum. It's important to understand that serum magnesium represents only about 1% of total body magnesium—the rest is in cells, bones, and tissues. The body tightly regulates serum magnesium, pulling from stores to maintain blood levels even when you're becoming deficient.
Because of this, serum magnesium is better at detecting severe or acute deficiency than mild or chronic insufficiency. If you have symptoms of magnesium deficiency but normal serum levels, consider RBC (red blood cell) magnesium for a more accurate assessment of your cellular magnesium status.
Price
$7
All-in
$25
incl. $18 lab & physician fee
Results
1 business days
Fasting
Not Required
What's Measured
What This Test Measures
This test measures magnesium concentration in blood serum, reported in mg/dL or mEq/L. Normal range is typically 1.7-2.3 mg/dL (1.4-1.9 mEq/L). Low serum magnesium (<1.7 mg/dL) indicates deficiency. Critically low (<1.2 mg/dL) can cause serious symptoms.
Who Should Consider This Test
People with muscle cramps or spasms, those with heart arrhythmias or palpitations, individuals on diuretics or PPIs long-term, diabetics (magnesium is commonly low), people with alcoholism, those with digestive conditions affecting absorption, and anyone with severe or acute symptoms suggesting deficiency.
Health Insights
Conditions Screened
Related Symptoms
When to Get Tested
No fasting required. Serum magnesium can be tested any time. Note that normal serum magnesium does not rule out deficiency—for a more comprehensive assessment, consider RBC magnesium.
No fasting needed. How to prepare for your blood test →
Understanding Your Results
Normal: 1.7-2.3 mg/dL. Low (<1.7 mg/dL): deficiency likely, may cause symptoms. Critically low (<1.2 mg/dL): severe deficiency, can cause dangerous heart rhythm issues. High (>2.6 mg/dL): usually from kidney failure or excess supplementation, can cause weakness and cardiac effects.
What to Expect
After placing your order, we send it straight to Quest Diagnostics — there is no consent form to sign and no partner email to wait for. Your requisition is usually ready to download from your dashboard within about an hour, and you can book your blood draw at any Quest Diagnostics location.
The blood draw typically takes just a few minutes. Results are usually available within 1 business days and will appear in your secure JustLabs dashboard.
Our results include reference ranges and easy-to-understand indicators showing whether your values are within normal limits.
How much does the Magnesium test cost?
The Magnesium test costs $7 at JustLabs — $25 all-in, since the $18 lab & physician order fee is charged once per order, however many tests you add. The price is fixed before your blood draw; no insurance or doctor visit needed.
| Option | Price | Order all-in | Notes |
|---|---|---|---|
| Magnesium at JustLabsDrawn at Quest Diagnostics | $7 | $25 | Includes the one $18 fee, charged once per order |
Paying with an HSA or FSA? See which lab tests qualify
Frequently Asked Questions
Hospital cash price: $100–$200
$7
+ $18 order fee · $25 all-inOne $18 fee per order covers your Quest blood draw and the independent physician order, however many tests you add.
- Results in 1 business days
- No fasting required
- Physician order included
No insurance needed · HSA/FSA eligible
- Physician-ordered
- CLIA-certified Quest lab
- Drawn at Quest Diagnostics
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