Magnesium Blood Test Cost and Medicare Coverage (CPT 83735)
Also called: serum magnesium · Mg test · magnesium level — all the same test, CPT 83735.
Regional policy — rules vary by state — examples on this page are from one region what's this?
This test is governed by Local Coverage Determinations (LCDs) — rules written by regional Medicare contractors, each binding only in its own territory. Every region keeps its own covered-diagnosis list, so the examples on this page (drawn from one region’s policy) may differ in your state. Want your state’s actual answer? Send us your codes — the free lookup checks the policy that applies to you.
- Does Medicare cover it?
- Only for certain diagnoses — such as low calcium or potassium being investigated, diuretics or certain heart-rhythm drugs, malabsorption or malnutrition (including alcohol-related), kidney disease and dialysis (examples only; details below)
- You pay if covered
- $0 — no deductible, no coinsurance
- Medicare pays the lab
- $6.70
- Information verified
- 2026-09-04
Buy it yourself — what you'd really pay
| Where | Test price | Fee | Total |
|---|---|---|---|
| Jason Health jasonhealth.com | $15 | $18 one fee per order — covers every test on it | $33 |
| Ulta Lab Tests ultalabtests.com Partner link — we earn a commission if you order. No extra cost to you. | $23.95 | $12.95 draw fee — one per order, covers every test on it | $36.90 |
| Quest questhealth.com | $39 | $6 physician service fee | $45 |
| Labcorp ondemand.labcorp.com | $39 | — | $39 |
Disclosure: the Ulta Lab Tests link above is a partner link. If you order through it, ClaraCover earns a commission. It costs you nothing extra, and it never changes what we tell you about Medicare coverage.
The short answer
Only when something in your situation genuinely depletes or disturbs magnesium — not “let’s check your minerals.” Regional Medicare policies cover the magnesium test for a specific set of conditions and medications known to drain it. Ordered that way, it’s covered and costs you $0. Ordered inside a wellness or nutrient panel for general interest — the way magnesium is most often marketed — it’s screening, and screening is denied. Medicare pays the lab just $6.70 for this test, a number worth remembering at any signature pad.
When Medicare DOES cover it
The covered picture (from one regional policy, LCD L36702):
- Electrolyte problems being investigated — low calcium or low potassium often travel with low magnesium, so an abnormal result on those triggers a covered magnesium check
- Medications that deplete magnesium — diuretics (“water pills”), certain heart-rhythm drugs (patients on those get magnesium checked about every 6 months), some chemotherapy and long-term acid reducers
- Conditions that drain it — malabsorption, alcohol-related malnutrition, poorly controlled diabetes, hyperparathyroidism
- Kidney disease and dialysis, where magnesium balance needs watching
- Symptoms of deficiency — muscle weakness, tremors, cramping, or heart-rhythm disturbances being worked up
- Long-term IV nutrition — checked monthly
When Medicare does NOT cover it
- Routine screening — magnesium “just to see,” with no qualifying condition, medication, or symptom
- Wellness and micronutrient panels — treated as screening categorically
If your test gets flagged, ask your doctor which covered situation applies to you. (Never ask anyone to change a code just to get coverage — that’s fraud. But doctors often have a legitimate reason for the test that simply wasn’t coded.)
What you pay if it IS covered: $0
Covered lab tests cost Medicare patients nothing — no deductible, no 20% coinsurance. Medicare pays the lab $6.70, and you owe zero.
What you pay if it is NOT covered — read this before you sign
- Ask the lab to print exactly what you would owe. You’re entitled to the number first. For perspective: Medicare pays the lab $6.70 for this exact test.
- Know the direct prices: $15 at Jason Health (jasonhealth.com — add their flat $18 lab-collection fee per order) and $39 at both Quest’s consumer site (questhealth.com, plus a $6 physician fee) and Labcorp OnDemand. Same certified labs, same blood draw.
Before you sign the pad — 60-second checklist
- Ask: “Can you print what I’ll owe if Medicare doesn’t pay?”
- Ask your doctor: “Which of my conditions or medications makes this test necessary?”
- Compare the printed price to the direct-purchase prices before deciding.
Quick questions people ask
What is the magnesium blood test called? You’ll see it written several ways: serum magnesium, magnesium level, Mg, or just “magnesium” on the lab slip — all the same test, CPT code 83735. (A different version, “RBC magnesium,” measures magnesium inside red blood cells — a separate test with a separate code that Medicare treats separately.)
What blood test checks magnesium — is it part of regular blood work? Not automatically. Magnesium is not included in the basic or comprehensive metabolic panels — it’s its own order and its own line on the bill, which is exactly how it ends up on a signature pad when the rest of the panel sails through.
Do you have to fast for a magnesium test? No — fasting isn’t required, though it’s often drawn with tests that do require it. Follow your order’s instructions.
Sources and data dates
Medicare payment amount: CMS Clinical Laboratory Fee Schedule, 2026 Q3 file (national rate). Coverage rules: CMS Medicare Coverage Database, LCD L36702 (a regional policy used here as the example — your region’s policy may differ in details). Consumer prices checked September 2026. Information current as of the date shown above; coverage is always determined by Medicare when your claim is processed.
ClaraCover provides information, not medical, billing, or insurance advice. Talk to your doctor about what tests you need.