National Institute on Aging:
Asking questions is key to good communication with your doctor. If you don't ask questions, he or she may assume you already know the answer or that you don't want more information.
Don't wait for the doctor to raise a specific question or subject; he or she may not know it's important to you. Be proactive. Ask questions when you don't know the meaning of a word (like aneurysm, hypertension, or infarct) or when instructions aren't clear (for example, does taking medicine with food mean before, during, or after a meal?).
Sometimes, doctors need to do blood tests, x-rays, or other procedures to find out what is wrong or to learn more about your medical condition. Some tests, such as Pap tests, mammograms, glaucoma tests, and screenings for prostate and colorectal cancer, are done regularly to check for hidden medical problems.
Before having a medical test, ask your doctor to explain why it is important, what it will show, and what it will cost. Ask what kind of things you need to do to prepare for the test. For example, you may need to have an empty stomach, or you may have to provide a urine sample. Ask how you will be notified of the test results and how long they will take to come in.