The osmolarity of normal human blood plasma is approximately 300 mosmoles per liter, with a general range of 285 to 310 mosmoles per liter. Osmolarity measures the concentration of solutes within a volume of water.
Common solutes in human blood plasma include electrolytes, sugars and amino acids. The greater the amount of solutes in the blood, the higher the osmolarity. A high osmolarity corresponds with a lack of water relative to the amount of solute in the blood, resulting in dehydration.
Both osmolarity and osmolality measure the concentration of solutes within a water solution. In osmolarity, the concentration is measured in moles per liter of solution. In osmolality, solute concentration is measured in moles per liter of water.