1. What is Serum Osmolality?

Serum osmolality is a measure of the concentration of dissolved particles in blood. It's important for evaluating fluid and electrolyte balance, and for diagnosing conditions like dehydration, diabetes insipidus, and toxic alcohol ingestions.

2. How Does the Calculator Work?

The calculator uses the standard serum osmolality equation:

Where:

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

Explanation: The equation accounts for the major osmotically active particles in blood. Sodium is doubled to account for associated anions.

3. Clinical Importance

Details: Serum osmolality is crucial for assessing water balance, diagnosing hyponatremia, evaluating mental status changes, and screening for toxic alcohol ingestion.

4. Using the Calculator

Tips: Enter sodium in mmol/L, glucose 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?
A: Normal range is typically 275-295 mOsm/kg. Values outside this range indicate potential disorders.

Q2: What is the osmolar gap?
A: The difference between measured and calculated osmolality. A gap >10 suggests unmeasured osmoles (e.g., ethanol, methanol).

Q3: Why isn't potassium included?
A: Potassium's contribution is small and relatively constant, so it's omitted from this calculation.

Q4: When is this calculation most useful?
A: Particularly valuable in evaluating hyponatremia, polyuria syndromes, and suspected toxic alcohol ingestion.

Q5: How does this differ from urine osmolality?
A: Urine osmolality measures kidney concentrating ability, while serum osmolality reflects overall body water balance.