1. What is Serum Osmolality?

Serum osmolality is a measure of the number of dissolved particles per kilogram of serum. It helps evaluate the body's water balance and is used to diagnose conditions like dehydration, water intoxication, and diabetes insipidus.

2. How Does the Calculator Work?

The calculator uses the serum osmolality equation:

Where:

• \( Na \) — Sodium concentration (mEq/L)
• \( Glucose \) — Blood glucose level (mg/dL)
• \( BUN \) — Blood urea nitrogen (mg/dL)

Explanation: The equation accounts for the major contributors to serum osmolality - sodium (and its accompanying anions), glucose, and urea.

3. Importance of Osmolality Calculation

Details: Serum osmolality is crucial for assessing fluid and electrolyte balance, diagnosing hyponatremia, and evaluating the effectiveness of treatment for various metabolic disorders.

4. Using the Calculator

Tips: Enter sodium in mEq/L, glucose in mg/dL, and BUN in mg/dL. All values must be valid (sodium > 0, glucose and BUN ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: What is a normal serum osmolality range?
A: Normal range is typically 275-295 mOsm/kg. Values outside this range may indicate fluid or electrolyte imbalances.

Q2: What is the osmolar gap?
A: The difference between measured and calculated osmolality. A gap >10 suggests the presence of unmeasured osmoles like ethanol or methanol.

Q3: Why is sodium multiplied by 2 in the equation?
A: Sodium is multiplied by 2 to account for its accompanying anions (mainly chloride and bicarbonate).

Q4: When should osmolality be measured directly?
A: When toxic alcohol ingestion is suspected or when the calculated osmolality doesn't match clinical findings.

Q5: How does hyperglycemia affect osmolality?
A: High glucose levels increase serum osmolality and can cause osmotic diuresis when severe.