Final answer:
The most appropriate instructions to give when a patient becomes dizzy when attempting to stand due to changes in blood vessels is to get up slowly.
Step-by-step explanation:
When a patient becomes dizzy when attempting to stand due to changes in blood vessels, the most appropriate instructions to give are to get up slowly. This allows the body time to adjust to the change in position and helps prevent a sudden drop in blood pressure in the brain. By getting up slowly, the blood vessels have a chance to constrict and maintain proper blood flow to the brain, reducing the risk of dizziness or fainting.