Final answer:
The nurse should provide information on increasing fluid intake following an upper gastrointestinal series with barium contrast.
Step-by-step explanation:
When providing discharge instructions to a client following an upper gastrointestinal series with barium contrast, the nurse should provide the information to increase fluid intake. This is because the barium contrast used in the procedure can cause constipation, and increasing fluid intake helps prevent it. It also helps to flush out any remaining barium from the system. Taking an over-the-counter antidiarrheal medication is not necessary, as the procedure is more likely to cause constipation than diarrhea. Black, tarry stools are not expected after the procedure, as they are usually associated with gastrointestinal bleeding. Following a low-fiber diet is also not necessary unless specifically instructed by the healthcare provider.