Arterial Blood Gas (ABG) Calculator

An arterial blood gas (ABG) test measures the acidity and levels of oxygen and carbon dioxide in your blood — this Arterial Blood Gas (ABG) Calculator interprets those values to identify acid-base disorders. Enter your pH, PaCO₂, and HCO₃⁻ to get the Primary Disorder, pH status, and compensation status. Optionally add Na⁺, Cl⁻, and Albumin to calculate the Anion Gap and expected compensation range.

Normal range: 7.35-7.45

mmHg

Normal range: 35-45 mmHg

mEq/L

Normal range: 22-26 mEq/L

mEq/L

For anion gap calculation

mEq/L

For anion gap calculation

g/dL

For corrected anion gap

Results

Primary Disorder

--

pH Status

--

Compensation

--

Anion Gap

--

Expected Compensation

--

More Chemistry Tools

Frequently Asked Questions

What are normal arterial blood gas values?

Normal ABG values are: pH 7.35-7.45, PaCO₂ 35-45 mmHg, HCO₃⁻ 22-26 mEq/L, PaO₂ 80-95 mmHg, and O₂ saturation 95-99%. Base excess should be within ±2 mEq/L.

How do I interpret ABG results step by step?

Follow these steps: 1) Check pH (acidotic <7.35, alkalotic >7.45), 2) Determine primary disorder (respiratory vs metabolic), 3) Assess compensation, 4) Check oxygenation status, and 5) Calculate anion gap if electrolytes available.

What is respiratory vs metabolic acidosis?

Respiratory acidosis occurs when CO₂ retention causes pH to drop (high PaCO₂, low pH). Metabolic acidosis results from loss of bicarbonate or gain of acid (low HCO₃⁻, low pH). The body compensates through breathing or kidney function respectively.

How does compensation work in acid-base disorders?

The body compensates for pH changes through opposite system responses. In metabolic acidosis, lungs hyperventilate to lower CO₂. In respiratory acidosis, kidneys retain HCO₃⁻. Full compensation normalizes pH, partial compensation improves but doesn't normalize it.

What is anion gap and why is it important?

Anion gap (Na⁺ - [Cl⁻ + HCO₃⁻]) helps classify metabolic acidosis. Normal gap is 8-12 mEq/L. High anion gap acidosis suggests unmeasured anions (ketones, lactate, toxins), while normal gap acidosis indicates bicarbonate loss or chloride retention.

When should I order an ABG vs venous blood gas?

ABGs are essential for assessing oxygenation and precise acid-base status in critically ill patients. Venous blood gases can assess acid-base status but cannot evaluate oxygenation. ABGs are preferred in respiratory failure, shock, or severe metabolic disorders.

What factors can affect ABG accuracy?

Air bubbles in sample, delays in analysis, improper storage temperature, and patient factors like fever or hypothermia can affect results. Samples should be analyzed within 15 minutes or kept on ice. Ensure proper arterial puncture technique and patient positioning.