indigestion
dyspepsia
stomach upset
upset stomach

And the first letter told me that he'd got stomach upset.

Find out ahead of time which foods make your stomach upset.

It may be taken with food if stomach upset occurs.

To decrease the chance of stomach upset, this drug is best taken with food.

If stomach upset occurs, you may take this drug with food.

You may take it with food if stomach upset occurs.

A stomach upset, most likely from too much ice cream last night.

You may take this drug with food to minimize stomach upset.

Stomach upset or discomfort, which is the most common side effect.

Fortunately, the average cold or stomach upset is nothing to worry about.