- 1). Check your birth certificate. In some areas, doctors will test a baby's blood type immediately after birth and will list it on your birth certificate.
- 2). Ask your parents. After trips to the emergency room when you were growing up, your parents may be able to tell you the blood type.
- 3). Call your doctor. Your medical records may indicate what your blood type is. You can call your doctor's office and speak with either the doctor or the nurse on duty, who can access your records.
- 4). Donate blood. When you donate blood, the Red Cross will put your blood through tests to determine your blood type. If you ask them to tell you what it is, they usually can after the tests. You may even automatically receive a card that tells you your blood type.
- 5). Guess your blood types based on your parents' blood types. Depending on your parents' blood types, you may be able to make a good guess. For example, if both of your parents have type O blood, you will certainly have type O blood. However, that is the only type you can guess with certainty--if your mother is type A and your father is type B, you could have any of the blood types.