Socialblood is trying to use Facebook’s vast network to connect such people to others who need their blood, and is one of a few growing ‘social-medicine’ technologies.

The idea is simple— the Socialblood website links to eight different groups on Facebook, one for each blood type. You can request to join the Facebook group for your own blood type and a moderator will approve your request. If ever you are in need of a blood donation, you can post a message to the group and potential donors who live in your vicinity can chime in to help.