from a musculoskeletal perspective, there is no difference to other clients. You do your assessment and make your exercise recommendations based on it.
There are different types of diabetes. People with type 1 diabetes have to monitor their glucose levels very carefully, what I have found, though, is that they are usually very well educated about the diabetes management.
Type 2 diabetes often occurs in people who are overweight, and in that case you may find other complications from a cardiovascular perspective.
In either case, I personally require a physician’s approval. I also make sure that the person understands the degree of diabetes management.
Hope this helps.