In 1999, Fitzpatrick embarked on a solo career under the name Vitamin C, releasing her eponymous debut album Vitamin C (1999), which was certified Platinum by the RIAA. Singles from the record include"Graduation (Friends Forever)" and the Top 20 single"Smile". Her second album, More (2001) spawned the singles"As Long as You're Loving Me" and"The Itch".
She appeared in the horror film Dracula 2000 (2000), and made cameo appearances in Get Over It (2001) and Scary Movie 2 (2001). She also appeared as a panelist on the spoof talent series The WB's Superstar USA in 2004. She was ranked No. 76 on the Maxim Hot 100 Women of 2001.
In March 2012, Fitzpatrick was appointed as Vice President of Music at Nickelodeon. Since early 2019, Fitzpatrick has served as a music executive for Netflix.