The 'Keeping Up with the Kardashians' star, who kicked her husband out of their house in Tarzana, California, in August after a failed intervention to get him to go to rehab, allegedly informed him on their fourth wedding anniversary last Friday (27.09.13) that she is preparing to file papers to formally end their marriage.
A source told Us Weekly magazine: ''She called him on their anniversary and told him she'd be filing for divorce. She wanted to give him fair warning. Khloe was very firm. She said she will be filing soon and she thinks it's best they move on.
''Khloe told Lamar she hopes he gets the help he needs.''
Khloe recently changed her name on her Instagram and Twitter profiles by removing her last name Odom.
The insider said: ''Changing her name on social media was a big step in letting people know she is moving on.''
Another source said that Khloe, 29, is still trying to get the basketball star, 33, to seek help even though she believes their relationship is over.
The friend said: ''She thinks he needs to be treated for this disease. (She) is really worried about his well-being and is afraid of what will happen to him.''
Lamar, who is allegedly addicted to crack cocaine, was accused of cheating on Khloe with several women earlier this year but she has stuck by him until now and has continued to wear her wedding ring.
The actress spoke about raising her 11 year old daughter Matilda in the wake of Heath Ledger's death eight years ago.