If you have A negative blood you can donate to anyone with a blood type of A or AB regardless of the positive or negative, however if you have A negative blood you can only receive A- or O- blood.
Understanding Blood Transfusions
There is a specific guideline in which blood transfusions must be conducted in order to be safe and successful. Transfusions must be matched appropriately to avoid dangerous outcomes. The breakdown is as follows:
Type A+ can donate only to A+ and AB+; can only receive from A+, A-, O+, and O-
Type A- can donate only to A+, A-, AB+, and AB-; can only receive from A- and O-
Type B+ can donate only to B+ and AB+; can only receive from B+, B-, O+, and O-
Type B- can donate only to types B+, B-, AB+, and AB-; can only receive from B- and O-
Type AB+ can donate only to AB+; can receive from all blood types
Type AB- can donate only to AB+ and AB-; can only receive from A-, B-, AB-, and O-
Type O+ can donate only to blood types A+, B+, AB+, and O+; can only receive from O+ and O-
Type O- can donate to all blood types. It is known as the universal donor type; can only receive from O-