| Oximetry Oximetry is a procedure used to measure the oxygen level—or oxygen saturation—in the blood. |
| Osmolality (Blood) This test measures the concentration of dissolved particles, or osmolality, in your blood. |
| Osmolality (Stool) This test measures the concentration, or osmolality, of certain particles in a sample of your watery stool. The test is used to find out why you have chronic diarrhea. |
| Osmolality (Urine) This test measures the concentration of particles in your urine. It finds out whether your electrolyte balance is normal and whether your kidneys are working properly. |
| Ova and Parasites (Stool) This test looks for parasites and their larvae or eggs in a sample of your stool. |
| Oxalate (Urine) This test checks for the chemical oxalate in your blood. High levels of this substance can make it more likely that you will develop kidney stones. |