Poor sleep affects our mental health and increases the risk of diabetes, heart disease, cancer and impotence in men, according to doctor and author Michael Mosley.
One way to test is to see if you are sleeping well enough is to test how long it takes to fall asleep in the middle of the day - falling asleep within 15 minutes indicates poor sleep, according to Mosley.
In the video, Michael Mosley explains how the experiment works.