# 🩸 BLOOD ## Human donation About 37% of the U.S. population is eligible to donate blood, but less than 10% of those eligible actually donate annually. This means that only a small fraction (~3%) of the population contributes to blood donations each year. You must wait a minimum of 56 days between whole blood donations. For platelet donations, you can donate once every 7 days and up to 24 times a year. O-negative blood is considered the most important for donations because it is the universal donor type, meaning it can be transfused to patients of any blood type, especially in emergencies. O-positive blood is also in high demand as it can be given to anyone with a positive blood type. Human blood falls into four different blood groups: **A, B, AB and O.** Your blood also has an Rh factor — short for rhesus. Blood contains a certain protein or it doesn’t. This is the positive [+] or negative [-] after your blood type. If your blood has the Rh factor, you’re Rh positive; if your blood lacks the Rh factor, you’re Rh negative. There are eight common blood type combinations: A positive, A negative, B positive, B negative, AB positive, AB negative, O positive, and O negative. ## Pet Blood Pets need blood donation. Animal blood and plasma cannot be stockpiled indefinitely, and there are no large commercial "Red Cross" facilities for pets, many local clinics rely on voluntary donors. Often vets and techs bring their own healthy dogs and cats to work to act as on-call donors ### Cat blood Cats have three main blood types: A, B, and AB. Type A is the most common, while type B is more prevalent in certain breeds, and type AB is quite rare. ### Dog blood Dogs have seven main blood types, known as Dog Erythrocyte Antigens (DEA), with DEA 1.1 being the most significant due to its potential to cause severe transfusion reactions. The blood types include DEA 1.1, DEA 1.2, DEA 1.3, DEA 3, DEA 4, DEA 5, and DEA 7, and dogs can be either positive or negative for these types. ## Horseshoe Crab Blood