Osmolality Calculator
Calculate serum osmolality, effective osmolality (tonicity), and osmolar gap for metabolic evaluation and toxic ingestion workup.
Important Health Disclaimer
This calculator provides general health information based on standard medical formulas and WHO guidelines. Results are for informational and educational purposes only and should not be considered as professional medical advice, diagnosis, or treatment recommendations.
For health concerns, medical conditions, fitness plans, or dietary decisions, please consult with qualified healthcare professionals, licensed physicians, registered dietitians, or certified fitness trainers who can evaluate your individual health status and medical history.
Individual health needs vary significantly. These calculations are general estimates and may not be appropriate for everyone, especially those with existing medical conditions, pregnant women, children, or elderly individuals.
Not a substitute for professional medical advice
Lab Values
Normal: 135-145 mEq/L
For osmolar gap calculation
To account for alcohol contribution
Calculated Osmolality
291 mOsm/kg
Normal
Osmolar Gap: Normal
Normal osmolar gap (-10 to +10 mOsm/kg)
Osmolality Formulas
Calculations
Osm = 2 × Na + (Glucose/18) + (BUN/2.8)
Effective Osm = 2 × Na + (Glucose/18)
Osmolar Gap = Measured - Calculated
Causes of Elevated Gap
- Methanol poisoning
- Ethylene glycol poisoning
- Isopropyl alcohol
- Mannitol administration
- Contrast agents
- Severe ketoacidosis
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