Hi, Blood donation is a noble gesture and donating it at three month interval is completely safe. It is in no way related to your weakness and hair fall. Hair fall could be associated with weakness due to underlying nutritional deficiency. This type of hair fall is diffuse and is known as telogen effluvium. I would advise that you get your serum ferritin, hemoglobin, thyroid profile and vitamin D level done. Another cause could be androgenetic alopecia. In this type of hair fall frontal, temporal and central area of scalp lose hair. I would advise that you consult a dermatologist and a physician to rule out the cause of hair fall and weakness. Hope that helped. Take care