Robin Roberts, Good Morning America: Roberts to go on medical leave again for bone marrow transplant

Robin Roberts returned to her "Good Morning America" co-anchoring role on Monday.

Roberts has declared that her health is much better now. However, she said she will again have to take medical leave to have a bone-marrow transplant from her sister.

Doctors are hoping that the bone marrow transplant can help her battle with MDS.

GMA posted on its Facebook page in advance that Roberts would return to the show Aug. 20.

The show also shared a message from Robin about her health:

Received a really good report from my doctor today. All my blood counts are up! The pre-treatment is doing its job and resting as I have lately has helped too. I've been given medical clearance to fly to Tuscany tomorrow for a friend's 50th birthday celebration.

When I return the following week I will have another bone marrow test to finally determine the timing of my transplant. Still slated for the end of the month or early September. That's when my lengthy medical leave will begin.

But all I'm thinking about now is Italy. As a going away present my doctor surprised me and removed my PICC line today from my arm...sweet freedom!

Thank you again for the prayers and well wishes...means more to me than you could possibly ever know.

Ciao! XO

Roberts announced on June 11 that she was diagnosed with MDS, or myelodysplastic syndrome, a rare disease of the blood and bone marrow.

She told viewers she may have to miss days here and there before taking an extended leave after a bone marrow transplant.

Amy Robach has been filling in for Roberts. Robach joined ABC News in May after more than nine years with NBC News.