A normal glucose does not exclude ketoacidosis

Euglycaemic ketoacidosis is the presentation that gets missed, and the reason is procedural rather than clinical: the glucose comes back at 11 mmol/L, the acidosis gets attributed to something else, and nobody sends ketones. It is seen with SGLT2 inhibitors, in pregnancy, after bariatric surgery, with prolonged fasting or vomiting, and in anyone carbohydrate-restricted who is also insulin-deficient.

The rule that catches it is simple. In any patient with diabetes who has an unexplained metabolic acidosis, a raised anion gap, or who is vomiting and unwell, measure ketones — capillary beta-hydroxybutyrate if you have it, urine ketones if you do not — whatever the glucose is. A beta-hydroxybutyrate above 3.0 mmol/L with acidosis is ketoacidosis regardless of the number next to it.

The second half of the rule concerns treatment. Euglycaemic ketoacidosis still needs insulin, which means it also needs glucose running alongside to allow the insulin to be given. Withholding insulin because the glucose is normal is the error that turns a recognised case into a prolonged one.

• Send ketones on any unwell patient with diabetes and an unexplained acidosis, whatever the glucose
• Ask specifically about SGLT2 inhibitor use — patients often do not list it among 'diabetes tablets'
• Stop the SGLT2 inhibitor during acute illness, fasting, and before surgery
• Treat with insulin plus concurrent dextrose; do not wait for the glucose to rise
• Give every patient on an SGLT2 inhibitor sick-day rules at the first prescription, and repeat them at review

Why it matters

The commonest reason euglycaemic ketoacidosis is missed is that nobody ordered the test that would have found it.

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