In patients developing sudden lack of efficacy, defined by a decrease in haemoglobin (1-2 g/dl per month) with increased need for transfusions, a reticulocyte count should be obtained and typical causes of non-response (e.g. iron, folate, or Vitamin B12-deficiency, aluminium intoxication, infection or inflammation, blood loss, and haemolysis) should be investigated.
Patsientidel, kellel avastatakse äkiline ravitoime langus, mis ilmneb hemoglobiini languses (1- 2 g/ dl kuus) ning on vajadus vereülekandeks, peab olema retikolotsüütide arv taastatud ja tüüpilised mittemõjumise põhjused (näit.