Lindsay Lohan is "scared" at the prospect of being sent back to jail.

The troubled star - who served just 13 days of a 90-day prison sentence in July after violating the conditions of her probation for a 2007 driving under influence (DUI) conviction - could return to prison after recently failing a court-ordered drugs test.

Friends of the 24-year-old actress have revealed the prospect of being incarcerated again has been a real "wake-up call" to Lindsay.

An insider explained: "She's scared she might have to go back to jail. This is a wake-up call for her in a way. In the past, she dismissed everything, never took it seriously and now she's like 'Oh, something bad could happen.'

"Her true friends are actually happy this is happening. They never knew what it would take for Lindsay to listen. This might be it. But still, the attitude of some of her friends is, 'Oh no, not again.' It never ends with her."

Despite the 'Mean Girls' star reportedly testing positive for cocaine and amphetamine abuse, experts believe Los Angeles Superior Court Judge Elden Fox could order Lindsay - who spent 22 days in rehab following her jail term - back to the rehabilitation facility, instead of to prison.