(CNN) -- Beyoncé is on the rebound after canceling a concert Tuesday due to "dehydration and exhaustion."
In a letter on her website, the 31-year-old entertainer apologized to her "dearest fans" in Antwerp, Belgium, who missed out on seeing the singer perform yesterday.
"I've never postponed a show in my life," Beyoncé wrote. "It was very hard for me. I promise I will make it up very soon. I'm sorry if I disappointed you."
Bey called off the show under advisement from her doctors, who told her she needed to rest. Thanks to the timing, the announcement fueled speculation that the star is expecting her second child with husband Jay-Z, with whom she has a toddler, Blue Ivy.
Beyoncé made no mention of the pregnancy rumors in her apology note, but thanked her fans for their concern.
"I'm feeling much better now, and I'm ready to give you a great show," she said, confirming that Wednesday's performance in Antwerp will carry on uninterrupted.
The May 14 concert will be rescheduled, and those with tickets have been instructed to hold on to them for the new show date. Other stops on Bey's "Mrs. Carter Show" tour aren't expected to be affected