Robin Roberts may have had to leave Good Morning America mid-broadcast Tuesday to deal with unexpected health concerns, but the ABC anchor is assuring fans that she's doing just fine.

"Feeling much better," Roberts, 51, tweeted one day after she announced midway through GMA's morning show that she was taking a few weeks off to deal with side effects of myelodysplastic syndrome (MDS), which she was diagnosed with in June. "Thanks for all the prayers & well wishes..same to you. Never appreciated vacation more. XO"

PHOTOS: Celebrity health scares

Suffering a sore jaw as a result of her treatment for the blood and bone-marrow disease, Roberts left GMA in the capable hands of her colleague Josh Elliott Tuesday, but not before cracking a few jokes when she had trouble pronouncing a word. "I can't talk on this side of my mouth," Roberts admitted. "We're going to miss you, but we do appreciate the Jimmy Cagney impersonation before you leave," Elliott kidded back.

PHOTOS: Most stylish TV anchors

The veteran ABC anchor -- who battled breast cancer five years ago -- is set to undergo a bone-marrow transplant this fall. Her sister is expected to be her donor. "I am very fortunate to have a sister who is an excellent match," Roberts has said. "This greatly improves my chances for a cure."

This article originally appeared on Robin Roberts Thanks Fans for "Prayers and Well Wishes" After Falling Ill During GMA