Final answer:
The nurse is focusing on the potential problem of dehydration for the client with diabetes mellitus and hyperglycemia.
Step-by-step explanation:
The nurse is focusing on the potential problem of dehydration for the client with diabetes mellitus and hyperglycemia. High blood glucose levels can make it difficult for the kidneys to recover all the glucose from urine, resulting in glucose loss and increased urine production. This can lead to dehydration, as the body loses water through urine.