1. What Is A Normal Calculated Osmolality Blood Test?

Calculated serum osmolality is a measure of the concentration of dissolved particles in blood. The normal range is 275-295 mOsm/kg. This test helps evaluate fluid and electrolyte balance, and detect conditions like dehydration, diabetes insipidus, or toxic alcohol ingestion.

2. How Does The Calculator Work?

The calculator uses the osmolality equation:

Where:

• \( Na^+ \) — Serum sodium concentration (mmol/L)
• \( Glucose \) — Serum glucose concentration (mg/dL)
• \( BUN \) — Blood urea nitrogen concentration (mg/dL)

Explanation: The equation accounts for the major contributors to serum osmolality. Sodium (with its anions) is doubled to account for both cations and anions.

3. Importance Of Osmolality Calculation

Details: Osmolality helps assess hydration status, diagnose electrolyte imbalances, and detect osmolar gaps (difference between measured and calculated osmolality which may indicate toxins).

4. Using The Calculator

Tips: Enter sodium in mmol/L, glucose and BUN in mg/dL. All values must be valid positive numbers. Normal range is 275-295 mOsm/kg.

5. Frequently Asked Questions (FAQ)

Q1: What causes high osmolality?
A: Dehydration, hypernatremia, hyperglycemia, uremia, or ingestion of alcohols like ethanol, methanol, or ethylene glycol.

Q2: What causes low osmolality?
A: Hyponatremia, overhydration, or SIADH (syndrome of inappropriate antidiuretic hormone secretion).

Q3: When is osmolality testing needed?
A: When evaluating altered mental status, suspected water balance disorders, or possible toxic alcohol ingestion.

Q4: What's the osmolar gap?
A: Difference between measured and calculated osmolality. Normal gap is <10 mOsm/kg. Increased gap suggests unmeasured osmoles (e.g., alcohols).

Q5: How does this differ from urine osmolality?
A: Urine osmolality measures kidney's concentrating ability, while serum osmolality reflects body fluid tonicity.