“I’ve had a sickness bug and barely kept fluids down — a blood test says my kidneys are off”

A rise in creatinine after a DEHYDRATING illness (diarrhoea/vomiting, poor intake) in a patient on an ACE INHIBITOR/ARB and an NSAID is the classic recipe for pre-renal ACUTE KIDNEY INJURY — the "triad" of ACEi/ARB + NSAID + intercurrent illness/dehydration — a common, often reversible, but dangerous problem. Assess severity (creatinine rise against baseline — NICE NG148: 26 micromol/L or more within 48 hours or 50% or more within 7 days — and the potassium, with a urine dipstick and, on an SGLT2 inhibitor, blood ketones per MHRA March 2020), hydration (postural dizziness and reduced URINE output/anuria by history; postural BP and dry mucosa need a face-to-face check) and RED FLAGS (confusion/drowsiness, fluid overload, features/risk of HYPERKALAEMIA — the dangerous electrolyte needing urgent K+/ECG — sepsis, and inability to keep fluids down), which determine home versus admission. The key examinable action is SICK-DAY RULES: temporarily STOP the medications that worsen AKI or accumulate during acute illness — ACEi/ARB, NSAID (stop and avoid), SGLT2 inhibitor (also euglycaemic DKA risk when unwell), metformin (accumulation/lactic acidosis risk in AKI) and diuretics — explaining to resume after 24–48 hours of eating and drinking normally (Think Kidneys 2018), with the ACE inhibitor restarted only once renal function has recovered. Manage hydration with oral rehydration if tolerated, but ADMIT for IV fluids/monitoring if the patient cannot keep fluids down or has severe AKI, hyperkalaemia, anuria, confusion or sepsis — and an older, diabetic patient on an SGLT2 inhibitor who is vomiting with postural dizziness needs same-day hospital assessment rather than a trial at home. Arrange to RECHECK U&E within a few days (and review restarting medications), and give clear FUTURE SICK-DAY guidance — pausing the listed drugs and seeking advice during any dehydrating illness, ideally on a sick-day card — while avoiding routine NSAIDs in at-risk patients. The hidden agenda is the patient not connecting her tablets/ibuprofen to the result; explain the link, institute the holds, decide disposition safely, recheck, and equip her for the future — not ignore the AKI or leave her on the offending drugs.