Final answer:
The client with rheumatoid arthritis prescribed methotrexate should be instructed to increase fluid intake for kidney health and to reduce the risk of side effects.
Step-by-step explanation:
The nurse should include in the teaching that the client with rheumatoid arthritis who has a new prescription for methotrexate should increase fluid intake. Methotrexate can be nephrotoxic, and it is important to stay hydrated to help the kidneys process the medication effectively. Furthermore, appropriate hydration can assist in reducing the likelihood of potential side effects such as kidney damage. There are no standard recommendations to avoid grapefruit juice, increase salt intake, or avoid aged cheese specifically associated with methotrexate therapy for rheumatoid arthritis.