GMA's Robin Roberts to begin medical leave this Friday

"Good Morning America" co-anchor Robin Roberts will begin her medical leave Friday as she prepares for a bone marrow transplant, she announced Monday.

Roberts, 51, said on the show that she will check into a hospital Tuesday, where she will have about 10 days of medical preparation before the transplant to treat her myelodysplastic syndrome.

"It still takes about 10 days after being admitted because there's some things that you have to go through before the transplant actually occurs," Roberts said on air Monday.

"I can't imagine not getting up and being here," she added.

Her sister, she said, is "a perfect match" to be a donor.

Robert announced in June that she had been diagnosed with MDS and was preparing for the transplant.

Diane Sawyer, Katie Couric and the women of "The View" are likely to are expected to contribute to during Roberts' absence, according to The Wrap.