She told the New York Post newspaper on Monday: "I got sick again, but I am all right."
Despite her illness, Lindsay has been working on 'Scary Movie 5' and enjoyed the experience as she got a lot of great advice from her co-star Charlie Sheen.
Speaking at the Size Matters party in Central Park on Saturday evening she said: "I have been really sick with pneumonia but I have been working. I have been shooting 'Scary Movie' with Charlie Sheen. He was really great to work with and gave me some good advice about surviving in this business."
It had previously been reported that Lindsay - who was hospitalised with exhaustion and dehydration in June when filming 'Liz & Dick' - had used her complaint of suffering from "walking pneumonia" to get out of filming 'Scary Movie 5'.
A source said: "Lindsay missed every meeting she had for the film, including script reads and wardrobe meetings.
"Then she missed her flight to Atlanta to shoot the movie. The producers had been getting signs Friday that she was a mess, and would not be fit to work.
"She is under contract - so to get out of it, she had to prove that she was sick. She tried to prove she has walking pneumonia."
Lindsay eventually filmed the role.