The four sleep stages: what happens while we sleep?

Have you ever woken up feeling refreshed and energised, yet on other days felt groggy despite a full night of sleep? If you are curious about your sleep and what the specific sleep stages are, you are not alone. Sleep is far more than simply switching off. It is a dynamic and carefully regulated process that supports your physical health, sharpens your thinking and strengthens your emotional balance. In this article, you will discover what happens during the different stages of sleep and why they matter for your wellbeing.

Table of Contents

• What are the four sleep stages?

• Tips for improving your sleep

• What can disrupt your sleep?

• How understanding your sleep can help you feel better

• Frequently asked questions about sleep

What are the four sleep stages?

A sleep cycle is the pattern your brain and body follow as you move through different stages of sleep during the night.

Each cycle has two main types of sleep: 

1. NREM sleep (non-rapid eye movement) 

2. REM sleep (rapid eye movement)

You begin with NREM sleep, which includes three stages. After completing these stages, you enter REM sleep. After REM sleep ends, you return to the NREM stages and the cycle repeats.

One full sleep cycle lasts about 80-90 to 100-120 minutes, and if you sleep for around eight hours, you typically go through four to five/six cycles per night.

Source: Cleveland Clinic, 2023; NHLBI 2022 

1. NREM sleep (non-rapid eye movement)  

NREM sleep can be categorized in three stages: 

Source:  Cleveland Clinic, 2023

2. REM sleep (Rapid Eye Movement)

Source:  Cleveland Clinic, 2023

Tips for improving your sleep

Improving your sleep is not only about getting more hours of rest, but about supporting healthy sleep habits. Here are some practical steps: 

• Maintain a consistent sleep routine (aim for 7-8 hours, fixed bedtime and wake-up time, leave bed if awake >20 minutes)

• Be mindful of food, caffeine, nicotine and alcohol (avoid heavy meals before bed; limit stimulants; alcohol may disrupt sleep later in the night)

• Create a cool, dark and quiet bedroom environment (reduce evening light and screen use; consider blackout curtains, earplugs or relaxation techniques)

• Limit daytime naps (keep under one hour and avoid late naps; planned naps may help night-shift workers)

• Stay physically active during the day (exercise regularly but not close to bedtime; spend time outdoors)

• Manage stress before bedtime (write down worries, plan ahead, stay organised and use relaxation techniques such as meditation)

Source: Mayo Clinic, 2024

What can disrupt your sleep?

Many everyday factors can shorten or disturb your sleep:

• Ageing (Less deep sleep and more light sleep, leading to easier awakenings)

• Medical conditions (Restless legs syndrome, bruxism, nocturia, heart, lung, hormonal or neurological problems)

• Medications (Some prescription drugs can affect sleep)

• Stress and anxiety (Worrying or rumination can make it harder to fall back asleep)

• Caregiving or parenting (Night-time responsibilities can disrupt sleep)

• Light exposure (Jet lag, shift work or irregular daylight exposure can disturb the body clock)

• Lifestyle habits (Irregular sleep schedules, alcohol, caffeine and screen use before bed)

• Sleep environment (Too much light, noise or a partner’s snoring)

Source: Sleep Foundation, 2025

How understanding your sleep can help you feel better

Each sleep stage has a specific function, from physical repair and immune support to memory processing. When your sleep functions properly, you wake up feeling refreshed, focused and ready for the day.

Understanding sleep and its different stages can help you to:

• Recognise why you may feel tired even after enough hours in bed

• Identify habits or patterns that disrupt your sleep

• Take practical steps to improve your sleep quality

If sleep problems continue, it may be worth exploring possible underlying causes. At Homed-IQ, we provide clear health information and convenient at-home tests to help you better understand your wellbeing. Improving your sleep starts with understanding it, and that is an important investment in your overall health.

Frequently asked questions about sleep

How many sleep cycles do you go through per night?

Most people go through four to five/six sleep cycles per night (Cleveland Clinic, 2023; NHLBI 2022).

Is it possible to skip a sleep stage?

According to sleep experts, not everyone moves through every stage of sleep each night. Some people may skip one or even two stages. However, in general, most people alternate between different levels of NREM and REM sleep throughout the night as part of their normal sleep cycle (Howland, J., 2018).

How can you tell if your sleep is healthy?

To assess whether your sleep is healthy, it is helpful to look at both sleep quantity and sleep quality.

Sleep quantity refers to how many hours you sleep each night. For most adults, this is ideally around eight hours.

Sleep quality, on the other hand, refers to how well you sleep. It focuses on whether your sleep is restful, uninterrupted and truly restorative, not just whether you spent enough time in bed. You likely have good sleep quality if you:

• Fall asleep within 30 minutes

• Wake up no more than once during the night

• Get the recommended amount of sleep for your age

• Fall back asleep within 20 minutes if you do wake up

• Feel rested and energised in the morning

Source: Sleep Foundation, 2025