Osmolality measures the amount of dissolved substances (e.g., sodium, potassium) in blood and urine. An osmolality test and calculated osmolal gap help determine if someone has ingested a toxin or has a water imbalance.
Ketones (ketone bodies) are byproducts of fat metabolism, and blood ketones tests are primarily used to screen for, detect, and monitor a serious, sometimes life-threatening condition called diabetic ketoacidosis (DKA).
Peritoneal fluid is the liquid in the space surrounding the organs in the abdomen. Lab tests performed on this fluid help diagnose the cause of ascites (fluid build-up) or peritonitis (inflammation of the peritoneum).