You are eligible to donate blood if you are between 18-60 years old, weigh at least 45 kilograms, have a hemoglobin level over 12.5 gm%, and it has been at least 3 months since your last donation. You should not donate if you have a fever or cold, are taking antibiotics or other medication, had surgery in the last 6 months, received a vaccination in the last 24 hours, were pregnant or miscarried in the last year, or have any other condition listed.