Most healthy adults aged 18 to 65 are eligible to donate blood, although specific criteria may vary by country or organization. Potential donors must meet certain health requirements, including weight, hemoglobin levels, and general health status. It is also important for donors to be free from any infections or illnesses at the time of donation. Some individuals, such as those with certain medical conditions or those who have recently traveled to specific areas, may be temporarily or permanently deferred from donating. Blood donation organizations typically provide guidelines and screening processes to ensure the safety of both the donor and the recipient.