There are different types of exams which may be required, depending on your age, health, and the amount of life insurance you are requiting to buy.
The paraded exam is performed by a medical nurse and may include drawing blood, asking some health questions, and taking your blood pressure.
There are also full physical examinations which may be required of you if you are purchasing a large amount of life insurance, or are over a certain age.
The medical exam tests check for signs of health issues, such as, high blood pressure, high protein levels or high cholesterol, diabetes, STD's, HIV/AIDS, any prescriptions drugs in your system, tobacco,nicotine, and any sign of illegal drugs, such as, marijuana, cocaine, or methamphetamine, among others.
The results of the medical exam, blood and/or urine tests are used to determine your health, and signs of chronic illness, and your life expectancy - how long you are expected to live.
The insurance company compares the results of the exam with the answers you gave on your application for life insurance. If there are any discrepancies, the insurer may charge a higher rate for your life insurance, lower the amount of life insurance they offer you, or decline you for life insurance.
If you do not agree with the test results, you may ask for another exam, blood or urine test.
Here is more information about life insurance medical exams and how they work.