1. What is Serum Osmolality?

Serum osmolality is a measure of the concentration of dissolved particles in blood. It helps evaluate the body's water balance and is particularly useful in diagnosing conditions like dehydration, diabetes insipidus, and toxic alcohol poisoning.

2. How Does the Calculator Work?

The calculator uses the serum osmolality equation:

Where:

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

Explanation: This equation calculates the estimated serum osmolality based on the major osmotically active particles in blood.

3. Importance of Serum Osmolality Calculation

Details: Serum osmolality measurement is crucial for assessing fluid and electrolyte balance, diagnosing hyponatremia, evaluating renal concentrating ability, and screening for toxic alcohol ingestion.

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 the normal range for serum osmolality?
A: Normal serum osmolality ranges from 275 to 295 mOsm/kg. Values outside this range may indicate underlying medical conditions.

Q2: Why is this called "without ethanol"?
A: This calculation excludes ethanol, which is important when specifically evaluating for toxic alcohol ingestion. Ethanol can significantly increase measured osmolality.

Q3: What is the osmolar gap?
A: The osmolar gap is the difference between measured osmolality and calculated osmolality. A gap greater than 10 mOsm/kg suggests the presence of unmeasured osmoles like methanol or ethylene glycol.

Q4: When should serum osmolality be measured?
A: It should be measured when evaluating altered mental status, suspected toxic alcohol ingestion, disorders of sodium balance, or diabetes insipidus.

Q5: Are there limitations to this equation?
A: This equation may not account for all osmotically active substances and may be less accurate in certain conditions like hypertriglyceridemia or hyperproteinemia.