Final answer:
If an elderly man with diabetes takes insulin but does not eat, ketoacidosis should be suspected.
Step-by-step explanation:
If an elderly man with diabetes takes insulin but does not eat, you should be suspicious of a condition called ketoacidosis. Ketoacidosis can occur when a person with diabetes does not have enough glucose in their body to provide energy, causing the body to break down fat for fuel. This process produces ketones, which can build up in the blood and lead to serious health complications. It is important to seek medical attention immediately if ketoacidosis is suspected.