Question: how do you find out if you're a bone marrow match?
Answer: You register with the NMDP online or in person at a donor center. You can find a center by calling the toll-free number 1-800-MARROW2.
You collect cells from your cheek with a cotton swab or provide a small blood sample. ... 
If an HLA match is made with a patient in need, the NMDP contacts you.