Whether or not you are required to take an exam will depend on your age, health, and the amount of life insurance you need, as well as, the insurance company's guidelines for an exam.
The medical exam is paid for by the insurance company.
The exam usually consists of a paraded examiner visiting you at your home or office and asking you some health questions and what medications you may be taking. In addition, the examiner will take your blood pressure, and a sample of your urine and/or blood.
It is best to have all information about your doctors and medications handy for the examiner.
In addition, don't exercise or drink any caffeine the day of the exam.
Here's an article that explains more about a life insurance physical examination and how it works, what to expect, and tips for preparing for your exam.