Order RBC Magnesium Blood Test from JustLabs for $15 ($33 all-in for a single-test order: $15 + one $18 lab & physician order fee per order). Price includes lab processing at Quest Diagnostics. No insurance required.
RBC (red blood cell) magnesium measures magnesium inside your cells, providing a more accurate assessment of your true magnesium status than standard serum magnesium tests.
Magnesium is essential for over 300 biochemical reactions in the body, including muscle function, nerve signaling, blood sugar regulation, blood pressure control, and energy production. Yet an estimated 50-60% of Americans don't get enough magnesium.
Why RBC magnesium is better than serum magnesium:
- Only 1% of body magnesium is in blood; 99% is in cells and bones
- Serum magnesium can appear "normal" even when you're deficient
- The body tightly regulates serum levels, pulling from cells and bones to maintain them
- RBC magnesium reflects what's actually available inside your cells
- Deficiency symptoms often correlate better with RBC than serum levels
If you've been told your "magnesium is fine" but still have symptoms of deficiency (muscle cramps, fatigue, anxiety, poor sleep), RBC magnesium may reveal the true picture.
Price
$15
All-in
$33
incl. $18 lab & physician fee
Results
2-3 business days
Fasting
Not Required
What's Measured
What This Test Measures
This test measures magnesium concentration inside red blood cells, reported in mg/dL. Optimal RBC magnesium is typically 5.0-6.5 mg/dL. Levels below 4.5 mg/dL suggest deficiency. Some integrative practitioners aim for the upper end of the range (6.0-6.5 mg/dL).
Who Should Consider This Test
Anyone with symptoms of magnesium deficiency despite "normal" serum levels, people with muscle cramps, headaches, or sleep issues, those with diabetes or metabolic syndrome, individuals on medications that deplete magnesium (PPIs, diuretics), and those with high stress or alcohol consumption.
Health Insights
Conditions Screened
Related Symptoms
When to Get Tested
No fasting required. RBC magnesium can be tested any time. If supplementing, continue as usual to see your levels on your current regimen. Retest 2-3 months after starting supplementation to assess improvement.
No fasting needed. How to prepare for your blood test →
Understanding Your Results
Optimal: 5.5-6.5 mg/dL. Adequate: 4.5-5.5 mg/dL. Low: <4.5 mg/dL. If deficient, magnesium glycinate, citrate, or threonate are well-absorbed forms. It takes weeks to months to replete magnesium stores. Retest in 2-3 months.
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 2-3 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 RBC Magnesium test cost?
The RBC Magnesium test costs $15 at JustLabs — $33 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 |
|---|---|---|---|
| RBC Magnesium at JustLabsDrawn at Quest Diagnostics | $15 | $33 | 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
$15
+ $18 order fee · $33 all-inOne $18 fee per order covers your Quest blood draw and the independent physician order, however many tests you add.
- Results in 2-3 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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$15
+ $18 order fee · $33 all-in