Khloe, 31, had been scheduled to promote her book Strong Looks Better Naked this week but had to axe scheduled meet and greets with fans on doctors' orders.
Big sis Kourtney, 36, told E! News: "She's good. She's okay. She's not feeling well but she's okay."
A source added: "[Khloe] has an minor infection and is being treated by her doctors. She is run down as she has been burning the candle at both ends. She will be fine but needs some rest."
It was suggested yesterday that Khloe picked up an infection while caring for estranged husband Lamar Odom at hospital.
An insider told People: "She's home on antibiotics and being closely monitored a doctor."
Khloe has been by her former husband's side ever since he was found unresponsive at a Nevada brothel on 13 October. She rushed to the hospital in Las Vegas to be with him, and since he's been transferred to a facility in LA, she's also been a frequent visitor.
They were married from 2009 until 2013 but as their divorce wasn't finalised by the time of his collapse, Khloe was able to make medical decisions in her role as legal life.
Divorce proceedings were halted while Lamar was in a coma, but Khloe has said the divorce will go ahead in the future and she is not reuniting with Lamar.