I've gotten sick at the outstation before. I woke up with the stomach flu (thought it was the Subway I ate then went to bed right away on a reduced rest) so went about my morning stuff thinking it would go away. By the time I got to the airport with the crew, I knew it was more than just a upset stomach. I forced everything down (and in...) for the trip back to base and then called in sick. They had to burn the standby, but that's what they are there for. Went home and spent the rest of the day paying homage to the porcelain god.

I would caution STRONGLY against giving the company a "heads up." While chances are the scheduler would appreciate it and that could be the end of it, if the wrong person gets a hold of that and it makes it back to your CP, you might get accused of "flying while unfit" and have to answer the usual "What if there was an emergency?" question. Remember, no good deed goes unpunished.

When in doubt, keep it simple. Get back to base, call in sick. But at the same time, if you are SO sick that you cannot continue, dont! It is a judgement call on a gray area.

Another one I've thought of, at my airline we sometimes do flying through other bases. Instead of just Base-Outstation-Base-Outstation, it may go Base-Outstation-Different Base. What if you trip doesn't send you back to your own base for a while? Things to consider.