Magnesium test cost in St. Louis, MO — inpatient
In St. Louis, MO-IL, 8 hospitals list a cash price for magnesium blood test as an inpatient: from $7.92 to $120.94, with a median of $91.08. The lowest listed price is at Ranken Jordan Home for Convalescent Crippled Children Hospital — $83.16 less than the median here. Across Missouri, the median is $36.63 at 30 hospitals.
Cash prices at 8 facilities across 8 cities for code 83735, as an inpatient (admitted to hospital) . Collected Sep 23, 2026; the hospital files themselves were last updated between Mar 16, 2026 and Apr 24, 2026.
Where each hospital's price falls
Each dot is one hospital's cash price on a scale from the lowest to the highest in St. Louis, MO-IL.
Hospitals, cheapest first
| Hospital | Cash price | List price | Insurers pay | Off list | File date |
|---|---|---|---|---|---|
| Ranken Jordan Home for Convalescent Crippled Children Hospital lowest Maryland Heights, MO · (314) 872-6400 Magnesium Level | $7.92 | $9.90 | — | 20% | Apr 24, 2026 source file |
| Ranken Jordan Home for Convalescent Crippled Children Hospital Maryland Heights, MO · (314) 872-6400 Magnesium, 24 Hour Urine | $20.15 | $25.18 | — | 20% | Apr 24, 2026 source file |
| Mercy Rehabilitation Hospital South Louis, MO MAGNESIUM | $23.22 | $23.22 | $23.22 | — | Mar 16, 2026 source file |
| Gateway Regional Medical Center Granite City, IL · (618) 798-3000 L910235 MAGNESIUM, URINE | $40.20 | $67.00 | $67.00 | 40% | — source file |
| St Josephs Hospital Hospital Sisters Third Order of St Francis Breese, IL · (618) 526-4511 ASSAY OF MAGNESIUM | $79.92 | $111.00 | $3.80–$111.00 | 28% | — source file |
| St Josephs Hospital of the Hospital Sisters of the Third Order of St Francis Highland, IL · (618) 651-2600 ASSAY OF MAGNESIUM | $102.24 | $142.00 | $8.84–$142.00 | 28% | — source file |
| St Elizabeths Hospital of the Hospital Sisters of the Third Order of St Francis O'Fallon, IL HC MAGNESIUM | $105.12 | $146.00 | $3.80–$146.00 | 28% | — source file |
| Hshs Holy Family Hospital Greenville, IL · (618) 664-1230 ASSAY OF MAGNESIUM | $114.48 | $159.00 | $3.99–$159.00 | 28% | — source file |
| Mercy Rehabilitation Hospital St. Louis Chesterfield, MO MAGNESIUM | $120.94 | $120.94 | $120.94 | — | Mar 16, 2026 source file |
| Gateway Regional Medical Center Granite City, IL · (618) 798-3000 Q442 MAGNESIUM | $206.46 | $344.10 | $344.10 | 40% | — source file |
Inpatient: lowest $7.92, median $91.08, highest $120.94 — a 15.3× difference within the same market.
As an outpatient, the same code is billed by 12 facilities here, median $56.58 — that is the price to compare if you are not being admitted.
Cash or insurance?
At 5 of 7 hospitals that publish insurer rates for this code here, the cash price is below the highest rate a health plan has negotiated, and at 1 it is below every plan's rate. If you have insurance but have not met your deductible, you usually pay your plan's negotiated rate, which falls somewhere in the "Insurers pay" column. Paying cash can cost less, but a cash payment usually does not count toward your deductible. Ask the hospital for both numbers before you book.
What it is
A magnesium test measures the level of magnesium in the blood. Doctors order it for muscle cramps or weakness, an irregular heartbeat, low potassium or calcium that does not correct, and for people on diuretics, long-term acid-reducing drugs or with kidney disease.
What the price covers
The price usually covers running the test. The blood draw (36415) is often billed as a separate line.