A hypnic headache is a rare Trusted Source type of headache that wakes people from sleep. They’re sometimes referred to as alarm-clock headaches. Hypnic headaches only affect people when they’re sleeping. They often occur around the same time several nights a week.

Reference :Written by Corinne O’Keefe Osborn, Medically reviewed by Daniel Murrell, MD, https://www.healthline.com/health/hypnic-headache , july 3rd,2019