Lake was born to Jill (a homemaker) and Barry Lake (a pharmacist), in Hastings-on-Hudson, New York, but was largely brought up by her paternal grandmother, Sylvia Lake, until Sylvia's death in 1978. Lake attended Ithaca College for one year.

Lake made her film debut as Tracy Turnblad, the lead character in John Waters's 1988 cult-classic Hairspray. Lake also starred in other Waters films including Cry-Baby (with Johnny Depp and Susan Tyrrell), Cecil B. Demented (with Melanie Griffith and Stephen Dorff), and Serial Mom (with Kathleen Turner and Sam Waterston). She starred in Mrs. Winterbourne with Shirley MacLaine and Brendan Fraser, Cabin Boy, Last Exit to Brooklyn, Cookie, and Inside Monkey Zetterland.

The show debuted in syndication on September 13, 1993, and ended first-run episodes on May 25, 2004. In 2000, Lake told Rosie O'Donnell in an interview that she had signed on for four additional years. Although Sony Pictures Television had many stations contracted through the 2004–2005 season, Lake decided to end the show in August 2004, citing (among other things) a Desire to spend time with her family. She moved from Los Angeles to New York to tape the 11th season of the show, then returned to California when taping was complete. Lake returned to the talk show platform when she hosted a second talk show which premiered in September 2012 and was cancelled after one season.

Lake met Illustrator Rob Sussman in October 1993, on Halloween. The couple married in Las Vegas on March 26, 1994. They have two sons: Milo Sebastian Sussman (b. March 22, 1997), and Owen Tyler Sussman (b. June 18, 2001), whose water birth was actually shown in The Business of Being Born, the documentary that she also produced. They both filed for divorce in August, 2003, and their divorce was finalized on February 25, 2005.

She joined the cast of the Vietnam War drama series China Beach as a Red Cross volunteer, Holly "the Donut Dolly" Pelegrino, for the show's third season. She also had a recurring role on the CBS sitcom The King of Queens as Doug's sister Stephanie. She guest-starred on television series including Drop Dead Diva and a voice role on King of the Hill, and starred in the television movie Baby Cakes. She had a cameo appearance in the 2007 remake of the original cult-classic Hairspray as a william Morris talent agent, and teamed up with star Nikki Blonsky (who played Tracy Turnblad in the 2007 movie musical remake) and Marissa Jaret Winokur (who played Tracy Turnblad in the Broadway musical based on the original 1988 film) to record "Mama I'm a Big Girl Now" for the Soundtrack. The song is played during the film's end credits. She later reunited with original Hairspray co-star Deborah Harry for the film Hotel Gramercy Park, which was released in 2008.

After her talk show had wrapped production on its final season, Lake went on to host the 2006 CBS limited series Gameshow Marathon, which re-created classic game shows with Celebrity contestants. She also signed a development deal with Gameshow Marathon production company FremantleMedia for other ventures, including creating and producing Future programs and projects. In October 2007, Lake appeared in the Lifetime TV movie Matters of Life and Dating. Lake also had a cameo in the 2007 film Hairspray as a talent agent and also sang "Mama I'm A Big Girl Now" with Nikki Blonsky and Marissa Jaret Winokur for the film's end credits. The Business of Being Born, Lake's documentary about home birth and midwifery, was released in limited markets on January 18, 2008. The film premiered at the Tribeca Film Festival and Red Envelope released the film in New York, L.A. and San Francisco in October; it also screened in Australia.

The Business of Being Born included footage and details of Lake's own "life-changing" home-birthing experience and followed a midwife going about her work. Tribeca called it "The Inconvenient Truth of Childbirth". Lake described it as her life's work for the last three years and expressed hopes that the film educated and empowered people to really know their choices in childbirth. She performed in the CBS television special Loving Leah in January of that year. Lake also jointly wrote a book on the world of natural childbirth and birthing options, along with Abby Epstein and Jacques Moritz, Your Best Birth, which was published by Wellness Central on May 1, 2009. Lake and Epstein also launched MyBestBirth.com, an online social network, powered by Ning, intended to allow parents and medical professionals to dialogue about varying birthing options and resources. Lake returned to television on May 11, 2009, succeeding Sharon Osbourne as host for the third season of VH1's Charm School. On November 10, 2010, Lake joined fellow talkers Phil Donahue, Sally Jessy Raphael, Geraldo Rivera, and Montel Williams as guests of Oprah Winfrey on The Oprah Winfrey Show, marking the first time those hosts ever appeared together on one show since their programs left the air.

On September 18, 2010, Lake's rented Malibu home was destroyed by a fire. She and her sons escaped without injury. On January 15, 2011, Lake finished in sixth place in the PokerStars Caribbean Adventure Luxury Ladies Poker Event, collecting $5,587 of the prize pool.

On April 20, 2011, Lake signed with Twentieth Television to develop The Ricki Lake Show, which premiered in September 2012. The new program has a more Oprah-like format than that of her former talk show. It was cancelled after one season. Lake won the Daytime Emmy for Outstanding Talk Show Host in 2013.

Ricki Lake was Lake's first daytime talk show and at 24, she was the youngest person at the time to host one (that record would later be broken by eight-year-old Philippine child Actress Ryzza Mae Dizon in 2013). The show specialized in topics involving invited guests and incorporated questions and comments from a studio audience.

Lake began dating Christian Evans in the summer of 2009. They became engaged in August 2011, and married on April 8, 2012. On 29 October 2014, Lake filed for divorce from Evans, citing "irreconcilable differences". In December 2014, however, they announced they had put their divorce on hold. The divorce was finalized in 2015. Christian Evans died on February 11, 2017.

On December 7, 2016, Lake made a cameo in the television musical Hairspray Live! On February 11, 2017, Lake appeared as a guest judge on the British talent show Let It Shine with Gary Barlow, Dannii Minogue, and Martin Kemp on the BBC. On February 17, 2018, Lake appeared on the British television show Through the Keyhole with Keith Lemon.

In March 2018 at SXSW, Lake and Epstein premiered their documentary film Weed the People, examining the use of cannabis as Medicine and its status as a Schedule I prohibited drug in the United States. The film focused in particular on the use of cannabis in the treatment of pediatric cancer.