Sodium (Na+) (mmol/L) Enter your serum sodium level (e.g., 140)

Glucose (mg/dL) Enter your blood glucose level (e.g., 90)

Blood Urea Nitrogen (BUN) (mg/dL) Enter your BUN level (e.g., 14)

Measured Osmolality (mOsm/kg) (Optional) Optional: Enter measured osmolality to calculate the gap

Quick Examples:

Normal Adult Values Hyperglycemia Case

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This calculator is a screening tool only, not a diagnostic instrument. It is not intended to replace professional medical evaluation. Consult a healthcare provider.

What Is Serum Osmolarity

Serum osmolarity is a measure of how many particles, such as salts and sugars, are dissolved in the liquid part of your blood. It shows how much concentration is in your blood compared to water. This number is important because it helps doctors see if your body has the right balance of fluids and chemicals. If the number is too high or too low, it may suggest a health issue that needs attention.

How Serum Osmolarity Is Calculated

Formula

The formula looks at the three main things that dissolve in your blood. First, it doubles the sodium level because sodium travels with other particles called anions. Second, it divides glucose by 18 to convert it to the same unit as sodium. Third, it divides BUN by 2.8 for the same reason. Adding these together gives an estimate of the total concentration.

Why Serum Osmolarity Matters

Knowing your serum osmolarity is important for checking your body's hydration and chemical balance. It helps doctors find issues like dehydration or kidney problems early. This number can also show how your body handles sugars and waste products.

Why Fluid Balance Is Important for Health

If the particles in your blood are out of balance, your cells can shrink or swell as water moves in or out. This can be dangerous for your brain and other organs. Tracking this number may help prevent serious problems caused by severe dehydration, high blood sugar, or kidney issues.

For High Blood Sugar

High glucose levels can significantly increase serum osmolarity. When blood sugar is very high, it pulls water out of cells and into the bloodstream. This calculation helps show how much high sugar levels may be affecting your fluid balance.

For Kidney Function

The kidneys filter waste products like BUN from the blood. If BUN levels are high, it may mean the kidneys are not working well. This calculator helps estimate how waste products contribute to the overall particle concentration in your blood.