No, employees are not required to take all of their FMLA leave at once. You could take three weeks to recover after a knee surgery, go back to work for a few days, discover you are having difficulties for which your doctor recommends more time off — and take another three weeks of leave. Or, you could use part of your leave for an illness, then use more another time when you need to stay home to take care of a sick family member. You can even potentially use FMLA intermittently to work partial work weeks until you’re able to resume full-time status.