Serum Osmolality/Osmolarity

Osmolarity = 2(Na) + glucose + urea

Affected by Sodium concentration, ratio of intracellular and extracellular water

DDx

• High → An extra osmotic agent is present (e.g. sugar)
  • !HONK/HHS (fix sugar = fix Na)

Correction

• Normal Saline → target Na
• IV hypotonic (Dextrose/D5W) → target glucose