Flu and laryngitis have caused Rihanna to cancel another stop on her tour.
The singer's representative said her Tuesday show in Baltimore would be postponed. Rihanna, 25, also canceled her Sunday show in Boston due to illness.
"I hate disappointing people that never ever let me down!! I'm so embarrassed about this! Thank you for your prayers and well wishes!" she tweeted on Sunday.
Rihanna's "Diamonds World Tour" launched in Buffalo, N.Y., on Friday.
Live Nation said in a statement that "Rihanna is still recovering." The concert promoter said fans "are instructed to retain their tickets pending rescheduling show date information."
The next date on her tour is Thursday in Philadelphia.
Rihanna is supporting her seventh album, "Unapologetic," which features the hits "Diamonds" and "Stay."