| I'm a nursing student.
Yes, a random glucose of 240 isn't diagnostic of diabetes (though a second one over 200 would make it diagnostic). Even if the patient was on steroids, diabetes would still be diagnosed. It would be called "steroid-induced" diabetes, but it would still require treatment, and monitoring. If someone on steroids or with an infection gets hyperglycemia, it's an indicator diabetes is there or on it's way. A person with totally healthy glucose metabolism can handle an infection or steroids without elevated glucose.
The thing that annoyed me most was the doctor's casual response to an obviously elevated bg. | 
