Mia Farrow disappointed about ending hunger strike early

Mia Farrow

told People magazine that she knew she couldn't sustain her hunger fast to draw attention to Darfur because she was getting weaker and weaker.

"I lost about 13 pounds," the 64-year-old actress and humanitarian told People.

She wanted to finish out the three-week strike, but had to end it on Friday, the 12th day, on her doctor's orders. "My doctor visited on Wednesday and told me to have sugar immediately because my blood sugar count dropped," Farrow says. "He said I could go into seizures."

In the final hours, she couldn't even stand up. "I got up out of bed and went down to my knees. My muscles were aching," Farrow said.

Farrow, a UNICEF Goodwill Ambassador, began her hunger strike on April 27 to protest the Sudanese president's expulsion of 16 aid agencies in Darfur.

"I was very disappointed," she said. "I am a very stubborn person and very determined. I had modified my goal from 21 days and really hoped that I would reach my goal of fasting for 16 days, which is the number of aid agencies expelled."

During the past 12 days, Farrow stayed closed to her bed, listening to classical music and reading books. "I watched 'Schindler's List' all the way through. Then I cried and cried," she said.

She's regaining her strength by eating oranges and drinking soup, but hasn't stopped thinking about the pain in Darfur.

"While a million people in Darfur are facing starvation, I have the ability to end my fast," she said. "These people do not have that option. If I have any use at all, it is to speak for them."