# Acid–Base Disorders: Use a Sequence

An apparently normal pH does not exclude serious mixed disease. Interpret trends, compensation, and the clinical mechanism together.

![Infographic: Acid–Base Disorders: Use a Sequence](https://urinenephrology.org/visual-reference/images/mastery-acid-base.png?v=20261003c)

## Identify the process

pH describes the net balance. Carbon dioxide and bicarbonate help identify the dominant respiratory or metabolic process, while mixed disorders can partly normalize the pH.

## Recognize danger

Severe acidemia with shock, arrhythmia, respiratory fatigue, or altered consciousness needs urgent assessment. Stabilization and investigation proceed together.

## Calculate before naming

Use AG = sodium − (chloride + bicarbonate), following the laboratory convention. Interpret the gap with albumin because hypoalbuminemia can conceal unmeasured acids. In metabolic acidosis, compare measured PCO2 with expected respiratory compensation; excess CO2 indicates an additional respiratory acidosis.

## Treat the driver

Restore perfusion when appropriate, treat infection or ketoacidosis, stop causal toxins, and address kidney failure or gastrointestinal losses. A buffer does not remove the cause.

## Follow the trajectory

Repeat gas and chemistry measurements according to severity. Improvement in pH can coexist with persistent lactate production, ketogenesis, or inadequate ventilation.

## Normal pH can conceal two disorders

A patient with vomiting and lactic acidosis may have near-normal pH because alkalosis offsets acidosis. The elevated anion gap still requires a cause. Read pH, PCO2, bicarbonate, gap, and compensation together; do not stop because the pH falls within its reference range.

## Source lessons

- [student guide](https://urinenephrology.org/mastery/acid-base/student-guide.html)
- [metabolic acidosis](https://urinenephrology.org/mastery/electrolytes-advanced/metabolic-acidosis.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.