--- title: Magnesium, RBC Test type: test id: magnesium-rbc url: "https://www.test-well.com/tests/magnesium-rbc" price_usd: 29.99 lab_fee_usd: 6 all_in_usd: 35.99 cpt: 83735 category: Vitamins & Nutrients sample: Blood draw fasting_required: false results_in: "5–9 business days" labs: - Quest - Labcorp - BioReference orderable: true reviewed_at: 2026-09-14 order_url: "https://www.test-well.com/cart?add=magnesium-rbc&utm_source=ai_agent&utm_medium=markdown" --- # Magnesium, RBC Test > Red-blood-cell magnesium — a more sensitive measure of your body's true magnesium stores than the standard serum test, measured from a standard blood draw. At TestWell it costs $29.99 plus a $6 lab fee, needs no fasting, and results post in 5–9 business days. Physician-authorized with no doctor's visit or insurance needed; draw at Quest or Labcorp. ## Key facts | Fact | Value | | --- | --- | | Price | $29.99 + $6 lab processing fee per order ($35.99 all-in for this test alone) | | CPT code | 83735 | | Sample | Blood draw | | Fasting | Not required | | Results | 5–9 business days | | Labs | Quest Diagnostics, Labcorp, BioReference (NY & NJ) | | Biomarkers measured | 1 | | Physician authorization | Included — no doctor's visit, referral or insurance needed | | Payment | Card, HSA or FSA; cash-pay only (no insurance billing) | ## What does the Magnesium, RBC test tell you? Red-blood-cell magnesium — a more sensitive measure of your body's true magnesium stores than the standard serum test. Magnesium, RBC measures the magnesium held inside your red blood cells rather than in the serum. Because most of the body's magnesium is stored intracellularly, RBC magnesium is considered a more sensitive indicator of long-term magnesium status and can reveal a deficiency even when a standard serum magnesium reads normal. It's often ordered by practitioners investigating fatigue, muscle cramps, poor sleep, anxiety, migraines, or irregular heartbeat when a serum test wasn't conclusive. **Clinical use:** Vitamin and nutrient testing identifies deficiencies that can drive fatigue, immune dysfunction, neurological symptoms, and long-term disease risk — and confirms that supplementation is working. ## Who should order it? Anyone with restrictive diets (vegan, low-fat, low-carb), malabsorption conditions, fatigue, hair loss, mood changes, or currently supplementing and wanting to verify dosing. ## Biomarkers measured - Magnesium, RBC ## Price by lab | Lab | Test price | All-in (with $6 fee) | Notes | | --- | --- | --- | --- | | Quest Diagnostics | $29.99 | $35.99 | Choose at checkout; walk-in patient service centers nationwide (not NY/NJ) | | Labcorp | $29.99 | $35.99 | Choose at checkout; walk-in patient service centers nationwide (not NY/NJ) | | BioReference (NY & NJ) | $29.99 | $35.99 | New York and New Jersey orders route here automatically | Rhode Island is not served. Prices are identical online and in the lab; no draw fee or physician fee is added. ## How much does a Magnesium, RBC test cost? A Magnesium, RBC test costs $29.99 at TestWell — $35.99 all-in when ordered alone, because the $6 lab processing fee is charged once per order, with no draw fee or physician fee added. Hospital outpatient labs typically bill around $95.00 self-pay for the same test, and often more. With insurance, what you pay depends on your deductible and your plan's negotiated rate; TestWell's price is fixed before the draw and is HSA/FSA-eligible. | Where you order | Price | One test, all-in | Notes | | --- | --- | --- | --- | | TestWell (drawn at Quest or Labcorp) | $29.99 | $35.99 | Includes the one $6 lab processing fee, charged once per order | | Hospital outpatient lab, self-pay (typical) | $95.00 | $95.00 | Reference figure; hospital charges vary widely by facility and are often higher | Lab test codes: Quest test code 623 · Labcorp test no. 080283 · BioReference code 1383-9. ## How do you prepare? No fasting required. ## Related conditions - Vitamin deficiency (E56.9) - Nutrient deficiency (E63.9) ## Common questions about the Magnesium, RBC test ### How long do Magnesium, RBC results take? Most Magnesium, RBC results are available in 5–9 business days after your specimen arrives at the lab. You'll get an email the moment results are ready, with everything viewable in your TestWell portal. ### What sample is collected for the Magnesium, RBC? Blood draw. Sample is collected at a Quest, Labcorp, or BioReference patient service center near you, or via at-home phlebotomy where available. ### How much does the Magnesium, RBC cost without insurance? On TestWell, the Magnesium, RBC is $29.99. Quest Direct lists comparable tests at $45. Walk-in hospital labs typically bill $95 or more without insurance. Insurance is not required — pay one all-in price. ### Do I need to fast before the Magnesium, RBC? No fasting required for the Magnesium, RBC. No fasting required. ### Where can I get the Magnesium, RBC done? The Magnesium, RBC is available at Quest and Labcorp patient service centers nationwide. Order online at TestWell, pick your preferred lab, and we'll generate a digital requisition for the location closest to you. ## How to order 1. Add to cart: https://www.test-well.com/cart?add=magnesium-rbc&utm_source=ai_agent&utm_medium=markdown 2. Create an account or sign in, confirm your state and preferred lab, pay by card, HSA or FSA. 3. A licensed physician authorizes the order (usually within minutes); the requisition arrives by email. 4. Walk into any Quest Diagnostics, Labcorp, BioReference (NY & NJ) patient service center — no appointment needed at most sites. 5. Results post to your TestWell portal in 5–9 business days with reference ranges and flags. ## Related - [Biotin (Vitamin B7)](https://www.test-well.com/tests/biotin) — $259.99 - [Calcium](https://www.test-well.com/tests/calcium) — $26.99 - [Copper](https://www.test-well.com/tests/copper) — $31.99 - [CoQ10 (Coenzyme Q10)](https://www.test-well.com/tests/coq10-coenzyme-q10) — $74.99 - [Folate (Vitamin B9)](https://www.test-well.com/tests/folate) — $32.99 - [All Vitamins & Nutrients tests](https://www.test-well.com/tests/category/vitamins-nutrients) - [Full test directory](https://www.test-well.com/tests/directory) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-14. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md Canonical page: https://www.test-well.com/tests/magnesium-rbc Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.