Patients over 10 years of age with cyanotic congenital heart disease (CCHD) risk developing significant glomerular proteinuria, a condition called cyanotic nephropathy. Even though the pathogenesis of glomerulopathy associated with CCHD is still unclear, a potential mechanism is hyperviscosity-induced decrease in peritubular capillary blood flow leading to an increase in glomerular capillary pressure, in turn resulting in proteinuria. Although angiotensin-converting enzyme (ACE) inhibitors have been traditionally used in the treatment of these patients with cyanotic nephropathy, they may, however, not be well tolerated. Here we present a case of an adult patient with CCHD who could not tolerate an ACE inhibitor but showed improvement and stabilisation of her renal function following treatment with repeated phlebotomies.