Rihanna was rushed to hospital suffering with ''exhaustion and dehydration'' yesterday (08.05.12).

The 'You Da One' hitmaker tweeted a picture of herself attached to a drip in a hospital after reportedly spending the night partying at the Met Gala in New York, MediaTakeOut.com reports.

However, after a brief stay in the undisclosed medical centre, she was discharged and allowed to fly back to her home in Los Angeles, arriving in California earlier this morning (09.05.12).

One reason why the 24-year-old singer - who pulled out of a 'Saturday Night Live' rehearsal last week due to her tiredness - may be suffering with exhaustion is her extensive workout regime, with her trainer Harley Pasternake claiming she will even hit the gym in the middle of the night if necessary.

He said: ''Rihanna looks amazing right now. I've put her on a special 25-minute-a-day workout that consists of five mini-workouts. She does it five days a week, wherever she is in the world.

''One of my trainers travels with her to ensure she does it, but as it only takes 25 minutes and can be done anywhere, it's easy for her to fit around her busy schedule and even her holidays.''