Sepp Blatter has been ordered by doctors to take five days off work after having a medical evaluation for stress.
The 79-year-old, currently suspended from his role as FIFA president, consulted a doctor after feeling unwell, and although no underlying problem was discovered he has been ordered to rest.
His personal adviser Klaus Stohlker told Press Association Sport: "He has been told to rest for the next five days. It is nothing dramatic, he has not been to hospital. I've spoken to him today and he says he will be back in his private office on Thursday."
Stohlker said that Blatter had been forced to cancel an interview with Swiss television that was planned for next week.
Blatter is at the centre of the biggest corruption crisis to hit FIFA - Swiss legal authorities have opened criminal proceedings against him in connection with a ?1.3million "disloyal payment" made to Michel Platini, and the sale of World Cup TV rights to disgraced former Caribbean football chief Jack Warner.
He and Platini are both under a 90-day suspension imposed by FIFA's ethics committee pending disciplinary hearings.
Blatter has established a private office outside of FIFA where he has been continuing to work, and an employee there suggested he looked unwell and should see a doctor, according to Stohlker.
His advisor added: "He is not the youngest these days and it has been a difficult time, but he told me he feels fine and the doctor has said he should take it easy for five days.
"He did have an interview with Swiss television planned for next week which we have had to cancel, which is why the news got out."