Hi @traceyaus, Welcome to Mayo Connect. I’ve not had experience with Gemcap but had my share of other forms of intense chemotherapy. What you’re experiencing isn’t out of the ordinary. Unfortunately, nausea and diarrhea can hit instantly in some cases. Hah, yes, and grumpiness is soon to follow…it’s hard to be all sunshine and roses when you feel like crud! While miserable at the time, the side effects do ease and if all goes as planned the drugs do the job of ridding your body of the cancer cells!
Your infusion team or oncology team should be on top of that for you by offering one or more of a variety of anti-nausea meds. Don’t try to be stoic! Take the meds.

I did a quick search through Connect to find a number of discussions and conversations with other members using Gemcap for various diagnoses. Here is the link for you:
https://connect.mayoclinic.org/search/
May I ask what type of cancer you’re being treated for?