SLC5A2 and heart failure: <h4>Background</h4>Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are cornerstone therapies for heart failure, but their safety in extreme clinical scenarios warrants careful evaluation.<h4>Case summary</h4>A 37-year-old woman with end-stage familial hypertrophic cardiomyopathy and MYH7 mutations developed recurrent hypoglycemia during dapagliflozin therapy.