The British star's strong run at the tournament came to an end after a three-set loss to the world number four on Wednesday (26.03.25) and she had to be assessed by a doctor as she felt "really dizzy" and "faint" in the sweltering Florida conditions.
Raducanu said: "I just felt really dizzy.
"I felt faint. I don’t know.
"It was very humid out there and we have a long wait, so maybe just an accumulation [of things], and just physical points as well and there were long rallies and heavy conditions.
"I don't know how I kind of regrouped in that second set, but in the third I definitely struggled a little bit."
Despite her loss, Raducanu has achieved her best run at a tournament since her famous US Open win in 2021 and she was praised for her performance by the victorious Pegula.
The American player said: "It was tough.
"I played a good first set, a little let down in the second, got it back, went up 2-0 in the tiebreak, but it kind of flipped.
"She started moving the ball really well, serving good... sometimes it just happens, but I just wanted to come out in the third really strong, really quick, and just kind of jump on her and not keep the third set too close."
Raducanu had recently credited her impressive run at the event to the "freedom" which she has been playing with on court.
She told Sky Sports: "I've come a long way in the last week, I think since Indian Wells I wasn't necessarily feeling great about my tennis, about everything.
"But this week I have some really good people around me, who I trust and who I have fun with off the court as well and that's extremely important, I think.
"For me who's just very expressive, when I play my best I'm definitely authentic, true to myself and creative.
"I feel when I'm boxed in into a regimented way, I'm not able to kind of express myself in the same way. I'm happy with how I've realised that this week as well."