“He was treated for normal food poisoning earlier today and he is back home,” his spokesman Denis Onyango told Reuters, adding that the illness was not severe.
Odinga, 72, recently formed a new opposition coalition called NASA with three other parties.
The political alliance has yet to name its flagbearer for the coming election but Odinga is seen as a strong contender to challenge Kenyatta who is standing for the ruling Jubilee coalition.
In the same poll, voters will also pick a new parliament and regional authorities. (Courtesy Reuters)