A patient preferably receives blood from his own blood group, but in acute situations there is sometimes no time to determine the blood group of the patient. Think of serious traffic accidents or disasters. Blood group O negative is therefore used relatively often in hospitals.
Blood group O negative is badly needed. For many patients donors with blood group O negative are of vital importance. Chances are four times larger that brothers and sisters of people with O negative have the same blood type. Are you not sure which blood type you have, but do you want to give blood? Then you are also very welcome.
Women are allowed to give blood a maximum of three times a year, men up to five times a year. How often you are called upon depends on the blood group that is needed at a certain time.