The model-and-presenter - who has been in rehab four times to be treated for addiction to painkillers - says once you have been an addict you never fully escape your demons and could relapse at any time.
She said: "Once you are an addict you will never not be an addict. You-ll be an addict until the day you die. I think about it every single day. People who say they don-t think aboutdrugs anymore are dirty liars who are probably still using."
If Kelly - the daughter of Sharon and notorious hellraiser Ozzy Osbourne - ever feels as though she is going to relapse again, she calls a sponsor to stop her succumbing to substance abuse.
She added to Stylist magazine: "I`m constantly checking myself and taking a moral inventory to make sure I`m on the right path. When I do feel down I call a sponsor and talk it through. There are so many things you can do to make sure you don`t do drugs. Doing drugs is the easiest option. It`s something you feel like you have to do and it can be dark and scary and when you give up you grieve the loss of that part of your life, but slowly and surely, through becoming clean, you start to feel normal again."
In her book `Fierce`, Kelly spoke candidly about how she became addicted to Vicodin by the time she was 17.
The star first experienced the effects of the strong opiate when she had her tonsils taken out at 13 and three years later she was taking up to 50 tablets a day.
Kelly wrote: "I was waking up and emptying six Vicodin into my hand. Soon I was taking 50 pills a day. Most people would overdose on 10. My friends called me `Noddy` because I fell asleep all the time.
"My parents suspected. Mum would say, `Darling, are you taking something? Please tell your mummy.` But I was good at lying."