The Cottagers manager was put on a drip feeding antibiotics into a vein after falling "very ill" on the morning of the fifth round FA Cup replay game against West Ham.
"The situation has not changed from yesterday. Chris is still receiving treatment and has had 24 to 48 hours' bed-rest," said a Fulham spokesperson on Thursday.
Assistant manager Steve Kean will remain in temporary charge of first team affairs until Colemans return.