O positive blood is a blood type within the ABO blood group sytem. This blood type belongs to the O group and is the most common blood type found globally. Those with O positive blood can donate blood to all positive blood types, including O positive, A positive, B positive and AB positive. O positive blood holders can only receive O positive blood in return.
Blood types are distinguished as positive and negative through the Rhesus factor, or RhD. The difference is based on a protein present on the cell surface of the blood cells. The O positive blood type accounts for 37 percent of the entire population. The fact that O positive blood can be donated to all RhD positive blood types means that O positive blood group holders can donate to 83 percent of the entire population. To determine the blood type, an individual needs to take a blood test. If a person wishes to donate blood to another person, the donor is required to have a blood compatibility test, and a cross-match must be found before a blood transfusion can be done. This cross-match prevents unexpected reactions in the recipient, such as pain, fever, dizziness and blood in the urine.