Jennifer Lawrence went to hospital for bad gas on Monday (19.11.13).

The 23-year-old beauty confessed to feeling unwell just hours before the big Los Angeles premiere of her new movie 'The Hunger Games: Catching Fire' earlier this week, but Jennifer was left red-faced when doctors diagnosed her with flatulence.

The candid star joked to David Letterman on 'The Late Show': ''I thought I had an ulcer and it turns out it was a 'falser!'

''I just had this really bad pain for, like, three weeks, and you can only s**t your pants so many times a day before you have to go to the emergency room, before you're like, 'I need to go to the hospital.' ''

The Oscar-winning actress powered through her red carpet appearance on Monday (18.11.13), but only after a visit to the doctor.

A source told the New York Daily News' Confidenti@l column: ''She had a brief doctor visit sometime before the premiere. She had cramps and stomach pain. Turns out it was gas.''

Honest Jennifer is never one to shy away from embarrassing topics and took her ailment in good stride.

Asked how she was feeling at the New York premiere of 'Catching Fire' last night (20.11.13), she quipped: ''Good ... just gassy.''