GSTM1 and Hypertension: 30% of all treated patients exhibited hypertensive reactions. During the Hb and hematocrit correction phase, there were more patients becoming hypertensive with SC EPO therapy than with IV EPO. This was not the case during the maintenance phase of treatment, however, SC EPO-treated patients did not complain about injection site pain and adverse reactions. The relationship between EPO treatment, development of hypertension and route of EPO administration is complex and multifactorial.