The exam includes taking a blood or urine sample which they send to a laboratory for testing. They may test your sample for legal and illegal drugs, including marijuana, cocaine, methamphetamine, as well as, other health issues like STD's, HIV/AIDS, high cholesterol, diabetes, etc.
The results of your drug testing will help the insurer determine if they should insure you for life insurance, what amount of coverage to offer, and how much to charge you for your life insurance policy.
If you do not agree with the results of the testing you may request a re-test; however, the insurer is not required to allow a second drug test, and they may or may not pay for it.
But, if you are denied life insurance coverage due to the results of your drug test you may apply for coverage with another life insurance company.
Here's how to learn about life insurance drug tests and how you may purchase life insurance without any drug tests required.