That 3am wake-up is one of the most common — and most exhausting — sleep disruptions in perimenopause, and there is a clear hormonal reason for it.

Cortisol naturally starts rising between 3 and 4am as part of the body’s process of preparing for the day. In a balanced hormonal state, progesterone acts as a buffer — it has calming, GABA-like effects that help you sleep through this cortisol rise. During perimenopause, progesterone is often the first hormone to decline significantly. Without that buffer, the cortisol surge wakes you up earlier than it should, and your mind becomes alert before your body is truly rested.

Hot flashes occurring at the same time compound the problem — a sudden rise in body temperature at 3am also triggers waking.

This is not insomnia in the classic sense of not being able to fall asleep. It is a specific pattern of early waking driven by hormonal disruption, and it responds differently to treatment.

Things that can help: keeping your room cool (below 20°C), avoiding alcohol in the evening (it fragments sleep in the second half of the night), and magnesium glycinate taken at bedtime (there is some evidence it supports sleep and reduces anxiety — avoid if you have kidney problems). If this pattern has persisted for three months or more, speak to a gynaecologist about whether progesterone or HRT might be appropriate — addressing the hormonal root often resolves this kind of waking when other strategies do not.