In diabetic ketoacidosis the blood pH is typically:

• A. Elevated pH with elevated bicarbonate.
• B. Normal pH.
• C. Low pH with low bicarbonate.
• D. Low pH with high bicarbonate.

Answer: (C)

In diabetic ketoacidosis, an accumulation of ketone bodies (beta-hydroxybutyrate and acetoacetate) creates a metabolic acidosis. These ketones are acids, and as the body buffers them, bicarbonate is consumed, so its level falls. The hydrogen ions from the ketones lower the pH, producing acidemia. So the typical pattern is a low pH with a low bicarbonate concentration, often with an elevated anion gap and a compensatory drop in CO2 from hyperventilation.

The other patterns don’t fit DKA: an elevated pH with elevated bicarbonate would indicate alkalosis, not the acidemia seen in DKA; normal pH would not reflect the acid load; and a low pH with high bicarbonate contradicts the expectation that bicarbonate is consumed buffering the ketoacids.