Exact limits can vary slightly by country and blood bank, but generally:

·       Age: Usually 18–60 or 65 years for whole‑blood donation. Some centres may accept 17‑year‑olds with parental consent, but the most common starting age is 18.

·       Weight: Often at least 50 kg for a standard 450 ml donation. Some centres may adjust volume for donors between 45–50 kg.

These limits are there to protect donors from losing too large a portion of their total blood volume. In all cases, the final decision is made by medical staff after checking your health, blood pressure and hemoglobin.