Yes, it is possible to have diarrhea when you first start to take probiotics. Probiotics alter the microbiome, so when they are first introduced, some people may experience temporary symptoms such as gas, bloating, diarrhea, and abdominal cramps. These symptoms will dissipate after a few days. There have been a few cases where diarrhea resulting from probiotic use may be a sign of more severe complications. Issues like sepsis and fungus in the blood may occur in people who are already severely ill or have compromised immune systems. For those with healthy immune systems, symptoms will be temporary. If diarrhea persists past a few days, it may be a good idea to stop the probiotic supplement.