A method for obtaining a stabilised suspension of red blood cells encapsulating an active ingredient, from resealed RBCs incorporating the active ingredient, the method comprising the incubation of the resealed RBCs in an incubation solution at an osmolality of no less than 280 m Osmol/kg, for a time of 30 minutes or more, the incubation solution being a solution that does not contain an agent which is denaturating for the RBC membrane, the liquid medium is then removed from the incubated suspension and the RBCs obtained are placed in suspension in a solution allowing the injection of the suspension in a patient. The suspensions obtained are particularly characterized by an extracellular haemoglobin level maintained at 0.5 or lower, in particular 0.2 g/dl or lower and/or a haemolysis rate maintained at 2 or less, in particular 1 % or less, at 72 h after placing in suspension in a preservation solution and at a temperature of between 2 and 8 °C.
