also known as Potassium in Red Blood Cells
| # | Retailer | Lab | Seen | Price | |
|---|---|---|---|---|---|
| 1 | DirectLabscheapest via Quest Diagnostics · seen today | Quest Diagnostics | today | $139 | order → |
| 2 | LabsMD seen today | — | today | $336 | order → |
| Vitamin B12 | 16 retailers | $10 |
| Magnesium RBC Test | 14 retailers | $8 |
| Ferritin | 14 retailers | $9 |
| Calcium, Ionized | 14 retailers | $18 |
| Iodine Test | 13 retailers | $30 |
| Selenium | 12 retailers | $12 |
| Iron Test | 11 retailers | $13 |
| Zinc, Blood Test | 11 retailers | $11 |