Why do I keep waking up at 3am?

The 3am wake-up is the most common sleep complaint there is, and it has structure. Your sleep runs in roughly 90-minute cycles, and in the second half of the night the cycles get lighter - so a small disturbance that would never wake you at 11pm easily wakes you at 3am. The disturbances have names, and the NHS lists the usual causes of insomnia: stress, anxiety or depression; alcohol, caffeine or nicotine; a room too hot or cold; noise; shift work and jet lag. Evening alcohol is the sneakiest - it sedates you at bedtime, then rebounds as it metabolises, fragmenting the second half of your night, which is why the 3am pattern is so regular after drinks. Stress does the rest: if you wake and immediately start running tomorrow's problems, your brain learns that 3am is worry time, and the habit reinforces itself. What actually works: protect the basics (cool dark room, no caffeine after lunch, no alcohol near bedtime), do not check the time - clock-watching feeds the anxiety loop - and if you are clearly awake after about 20 minutes, get up, keep lights low, and do something calm until drowsy; the NHS points to changing sleeping habits as the first-line fix. MedlinePlus notes stress is a leading cause of short-term insomnia, which usually lasts days or weeks and resolves as the stressor passes. Waking early and unable to return to sleep most nights for a month or more, especially with low mood, deserves a GP conversation. Pymander is a free AI doctor, 24/7 by text, that can help you build the reset.