The definitive diagnosis follows two tests which are carried out in a controlled environment such as a sleep clinic.
The first is a Polysomnography which is a test conducted through the night which measures sleep efficiency by way of wires connected from a computer to various parts of the body ,including the scalp, and a video camera. This can then provide results such as R.E.M. content, apnoea, restless leg syndrome. It is also a guide to be used in conjunction with the second test-Multi Sleep Latency Test (MSLT). This is conducted using the same wires and monitoring system but in intervals of 20 minutes throughout the following day. This gives results that outlines be how quickly a person goes to sleep (latency) and whether they have R.E.M. sleep. These results could lead to the diagnosis of narcolepsy, Sleep Apnoea, Idiopathic Hypersomnia, etc, or require further testing if sleep was normal.