British number one Heather Watson lost in the first round of the Australian Open after feeling light-headed and requiring treatment from the doctor.Watson, whose ranking plummeted after a bout of glandular fever in 2013, lost 6-4 6-0 to Tsvetana Pironkova.
The 22-year-old was confident it was not a return of glandular fever but said she often struggled for energy.
"I felt very light-headed and low on energy - it's a shame that it's today," Watson told BBC Sport.
"I get it sometimes. I'm going to go and see the doctor afterwards and see if there's anything I can do to help with times like these in the future.
"I think it's just one of these things that I have, girl things. It just happens."
Watson called for the doctor towards the end of the first set and was visibly struggling as Bulgaria's Pironkova, ranked 52nd in the world and a Wimbledon semi-finalist in 2010, won the last seven games.
It was in Australia two years ago that Watson first felt the signs of what proved to be glandular fever, and she was given a reminder of that moment on Tuesday.
"When he came on in 2013 it was the same thing. I couldn't really do much, not knowing at the time what it was.
"He said: 'We'll just do the same, give you some gels and you've just got to fight through it.'
"That's what I tried to do. I tried to play more aggressive so we wouldn't have too many long rallies, but I wasn't consistent enough."
She added: "I get this at different times. I have a day or two here and there where I feel like this.
"I'm going to see the doctor afterwards because I can't let this affect me any more. I've lost this week now."
Watson had been brimming with positivity on arriving in Melbourne fresh from winning her second WTA title in Hobart last week.
With a career-high ranking of 38, she had designs on improving her Grand Slam record, having never been past the third round.
"It's really frustrating, especially at the one time I really do want all my energy and to be 100%," said Watson.
"But it happens and you're dealt with different cards on different days and I should have dealt with it better. It's a real shame and it sucks."