Metabolic acidosis
A stepwise blood gas approach with compensation, the albumin-corrected anion gap, delta ratio and osmolar gap, then the causes, renal tubular acidosis and when bicarbonate helps.
Tier 1Condition
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Metabolic acidosis is a primary fall in bicarbonate (below about 22 mmol/L). Acidaemia (pH below 7.35) is the blood result; acidosis is the process.
- Work through the gas in order: pH, primary process, compensation, anion gap (corrected for albumin), delta ratio, then osmolar gap if the cause isn't obvious.
- High anion gap causes are mostly lactate, ketones, kidney failure and toxins. Normal anion gap causes are bicarbonate loss from the gut or kidney, or chloride gain.
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Sources
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney DiseaseKidney Disease Improving Global Outcomes (Kidney International), 2024
- Jung B et al. Sodium bicarbonate for severe metabolic acidemia and acute kidney injury: the BICARICU-2 randomized clinical trial. JAMA 2025;334(22):2000-10JAMA, 2025
- Jaber S et al. Sodium bicarbonate therapy for patients with severe metabolic acidaemia in the intensive care unit (BICAR-ICU). Lancet 2018;392:31-40The Lancet, 2018
- Juurlink DN et al. Extracorporeal treatment for salicylate poisoning: systematic review and recommendations from the EXTRIP workgroup. Ann Emerg Med 2015;66:165-81EXTRIP workgroup, 2015
- Periprocedural diabetic ketoacidosis (DKA) with SGLT2 inhibitor use in people with diabetes (alert update)AU/NZAustralian Diabetes Society, ADEA, ANZCA and NZSSD, 2023
- Berend K, de Vries AP, Gans RO. Physiological approach to assessment of acid-base disturbances. N Engl J Med 2014;371:1434-45New England Journal of Medicine, 2014
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Personal emails, About story and Australian-style copy