How do I interpret an ABG?

Follow a systematic approach: (1) Look at pH — acidemia ( 7.45)? (2) Identify the primary disorder — is the pCO₂ or HCO₃⁻ driving the pH change? (3) Assess compensation — is the other value moving in the expected direction? (4) Calculate anion gap if metabolic acidosis is present.

What are normal ABG values?

Normal ranges: pH 7.35–7.45, PaCO₂ 35–45 mmHg, HCO₃⁻ 22–26 mEq/L, PaO₂ 80–100 mmHg. Values outside these ranges indicate an acid-base disorder. The body compensates by adjusting the system not primarily affected.

What is Winter's formula?

Winter's formula predicts the expected PaCO₂ in a primary metabolic acidosis: Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 (±2). If the actual PaCO₂ matches, compensation is appropriate. If lower, there is a concurrent respiratory alkalosis. If higher, there is a concurrent respiratory acidosis.

Can there be mixed acid-base disorders?

Yes. Patients can have two or even three simultaneous acid-base disorders. Clues include: pH that is more extreme than expected for either disorder alone, pCO₂ that does not match expected compensation, or an anion gap that does not correlate with the bicarbonate change (delta-delta analysis).

Online Medical Tools — ABG Interpreter

Printed on 2/13/2026

For informational purposes only. This is not medical advice.

ABG Interpreter

Arterial blood gas (ABG) analysis is fundamental to assessing a patient's acid-base status and respiratory function. This interpreter analyzes pH, PaCO₂, and HCO₃⁻ to determine the primary acid-base disorder (respiratory vs. metabolic acidosis or alkalosis), assess the degree of compensation, and identify mixed disorders. It applies Winter's formula and other compensation rules.

Compare with Anion Gap

Formula: Systematic analysis using pH, PaCO₂, HCO₃⁻, Winter's formula, and compensation rules

Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.