At age 15, Allen spent four weeks at The Priory clinic under 24 hour watch after the singer, distraught over a breakup with a boyfriend, took an overdose and tried to cut her wrists. Allen told The Sunday Times that "In my teens I did experiment with drugs” and “I don’t know anyone now who isn’t a drug-taker, in recovery from drugs, or on prescription drugs".

In November 2007, the singer revealed that she has been diagnosed with a heart murmur. The singer sparked concern when she shed 19lbs (8.6kg) and dropped from a UK size 12 to a size eight in just six weeks. Allen explained the weight loss on cutting back on the "crap" she eats and going to the gym three times a week to do a "hardcore routine" as a reaction to the diagnosis.

Allen suffered a miscarriage on 16 January 2008 after returning from holiday with Ed Simons of The Chemical Brothers. The child would have been the first for both parties. The couple met in September 2007. The pregnancy was said to have