Osmolality measures the concentration of solutes in a fluid by looking at the number of particles per weight (kilogram) of fluid. Osmolarity evaluates the number of particles per volume (liter) of fluid.

What does osmolality calculation mean?

Osmolality is a measure of how much one substance has dissolved in another substance. The greater the concentration of the substance dissolved, the higher the osmolality. Very salty water has higher osmolality than water with just a hint of salt.

What does it mean when your osmolality is low?

“Osmolality” refers to the concentration of dissolved particles of chemicals and minerals -- such as sodium and other electrolytes -- in your serum. Higher osmolality means you have more particles in your serum. Lower osmolality means the particles are more diluted.