Platelet and cell stimulation lead to plasma membrane remodelling, resulting in phosphatidylserine (PS) externalisation in the outer leaflet of the membrane, associated with the shedding of PS-rich microparticles (MPs), and contributes to thrombin generation by promoting the assembly of coagulation enzyme complexes. A previous study assessed MP levels in haemophiliacs after haemostatic treatment. To further investigate in vivo membrane remodelling, MP levels and characteristics were studied in 79 haemophiliacs and in 62 non-haemophiliacs. Both groups showed heterogeneity in MP levels, with higher values in individuals <18 years. This finding should be considered when studying MP levels in individuals <18 years.