Osmolality Calculator
Enter the required values below to run the educational estimation.
What is Serum Osmolality?
Osmolality is a measure of the solute concentration of blood. It is primarily determined by sodium, glucose, and urea. These solutes pull water across cell membranes, regulating hydration and cellular volume.
Calculating Estimated Osmolality
The standard clinical equation doubles the sodium value (accounting for accompanying anions like chloride) and adds glucose (divided by 18) and BUN (divided by 2.8) to convert units. If alcohol is present, it is divided by 3.7 and added.
Clinical Application of Osmolality
Osmolality calculations help diagnose fluid balance disorders like diabetes insipidus, syndrome of inappropriate antidiuretic hormone (SIADH), dehydration, and help screen for poisoning by toxic alcohols.
When to Seek Urgent Medical Attention
- Severe confusion, stupor, hallucinations, or seizures.
- Extreme, unquenchable thirst accompanied by massive urine output.
- Severe dizziness, inability to stand, or fainting.
Frequently Asked Questions
Serum osmolality measures the concentration of dissolved solute particles in your blood plasma. Typical healthy ranges are 275 to 295 mOsm/kg.
The osmolal gap is the difference between measured osmolality (from a lab) and calculated osmolality. A gap above 10 suggest the presence of unmeasured toxins (like methanol or ethylene glycol).
