Most ketoacidosis on modern therapy is not a prescribing error. It is a patient who kept taking a drug through an illness that should have stopped it. The conversation that prevents it is short enough to fit in a routine review, and it is worth having with every patient on an SGLT2 inhibitor and every patient on insulin.
The sequence to teach is simple: acute illness or fasting → stop the SGLT2 inhibitor, never stop the insulin → drink and eat carbohydrate → check ketones, whatever the glucose reads → seek help if ketones stay raised or vomiting starts. The two errors that cause harm are stopping insulin because the patient is not eating, and reassuring themselves on a normal glucose reading while ketones climb.
Give it in writing, in the language the patient reads. A card in the wallet is more use than a paragraph in a discharge summary, and it works when the patient is unwell and the clinic is closed. Where a patient tests ketones at home, a check on an ordinary well day roughly once a week establishes what their baseline looks like, so a raised reading during illness is recognisable as abnormal rather than guessed at.
- Stop the SGLT2 inhibitor during acute illness, vomiting, fasting, alcohol excess, or before surgery
- Never stop insulin during illness — the dose may need to go up, not down, even when eating less
- Check ketones on symptoms, not on the glucose number; euglycaemic ketoacidosis reads normal on a meter
- Written card, patient's own language, kept with the medicines — not filed in a letter
- Restart the SGLT2 inhibitor deliberately after recovery, with eating and drinking re-established
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