Having been discharged for only two days, Amy Winehouse has gone back to hospital for ongoing treatment.
The 25-year-old singer spent the past week being treated at the London Clinic. She left the hospital on Friday, but checked back in Monday.
"She had a chest infection [last week] and underwent some tests to make sure nothing else was wrong," a source tells PEOPLE.
"She has been told to give up smoking and was initially struggling with that – she was covered in nicotine patches at one point," says the source. "But she is making an effort."

Britney Spears appears back to her beautiful best on her new album cover.
The 'Womanizer' singer has released the artwork for her upcoming record 'Circus' and is pictured wearing a strappy dress complete with glowing skin and flowing blonde locks.
'Circus' is set to hit stores on December 2 - Britney's 27th birthday - with the star set to embark on a world tour to promote it next year. The first single from the LP, 'Womanizer', has already caused a storm in the US, after topping the Billboard Hot 100 chart when downloads of the track exceeded 286,000 in its first week of release.
The success of the single makes it the first number one song for Britney in the US since her 1999 track 'Baby One More Time'.