In this case report, we describe the story of a 42-year-old woman on haemodialysis who presented a severe secondary hyperparathyroidism and hyperphosphataemia, despite a heavy drug treatment including 90mg cinacalcet, 3600mg calcium carbonate and 2700mg aluminium hydroxide per day. Confronted to an apparent resistance to the calcimimetic, the question was: is this a true drug resistance or a pseudoresistance with, as clinical consequence, either a further increase of the dose of cinacalcet or a parathyroidectomy. To answer this question, we have monitored for two months drug adherence to phosphate binders and cinacalcet using electronic pillboxes called Medication Event Monitoring System (MEMS) without modifying the drug prescription. Drug adherence monitoring has been associated with a rapid normalisation of all laboratory parameters suggesting that the inefficacy of the treatment was essentially due to a nonadherence rather than due to a true drug resistance. This observation reminds us that nonadherence is one of the most frequent causes of apparent drug resistance, which should be considered in all cases of nonresponse to therapy. This case also illustrates the usefulness of electronic monitoring to identify problems of drug adherence and hence to improve and sustain medication intake in patients, including those on dialysis.