Actress Kate Beckinsale turned into a "monster" during her recent hospitalisation after she was put on "crazy drugs" following the rupture of an ovarian cyst.

The Underworld star was placed under doctors' care in Los Angeles after suffering the horrific ordeal in late January (19), when she initially thought the pain was caused by her appendix - even though she had previously had that removed.

"I had my appendix burst before, and I thought it was that again, but it can't happen twice, apparently!" she quipped on U.S. morning show Live with Kelly and Ryan.

"It was an ovarian cyst, which was really painful... You go to hospital and then they give you crazy drugs which make you behave badly."

Kate believes the morphine she was given to alleviate the pain made her behave more erratically than most, because she maintains such a clean diet.

"I don't drink coffee or alcohol or anything, so the minute I'm given an IV (intravenous) drug, I become a monster!" she confessed.

The Brit reveals one of her uncharacteristic antics while high on morphine involved her bluntly commenting on her pals' appearances: "I had friends of mine come visit me in the hospital and I said, 'Oh, you look so good, you were looking tubby (chubby) a few weeks ago!'" Kate shared. "(I said) terrible things! It wasn't even true! It was just me saying nasty things!"

And that wasn't all: "Then (there was) a lot of dancing, trying to touch people's bottoms," the 45 year old recalled. "I mean, it was a lot!"

She behaved so badly during her recovery period, Kate is still unsure if she's heard the worst of her escapades.

She said, "I kept finding out what I'd done weeks later, and having to apologise!"

Kate has since bounced back from the health emergency, and has been busy promoting her new Amazon series The Widow.