🌞 Circadian Rhythm in Humans
Your circadian rhythm is your body’s internal clock — a roughly 24-hour cycle that regulates sleep, wakefulness, hormone production, and even body temperature. Understanding your circadian rhythm can help you improve sleep quality, productivity, and overall health.
What Is the Circadian Rhythm?
The circadian rhythm is controlled by a group of brain cells in the hypothalamus called the suprachiasmatic nucleus (SCN). This “master clock” responds to light signals from your eyes to help your body know when it’s time to be awake or asleep.
How the Circadian Cycle Works
- Morning (6–9 AM) – Light exposure triggers cortisol release to help you wake up.
- Midday (10 AM–2 PM) – Alertness and performance are usually at their peak.
- Afternoon Dip (2–4 PM) – Energy naturally declines; short naps may occur.
- Evening (6–9 PM) – Melatonin production begins as light fades.
- Night (10 PM–2 AM) – Deepest sleep and recovery occur.
- Early Morning (3–5 AM) – Body temperature is at its lowest.
🛌 Best Bedtime Calculator
Choose your desired wake-up time and this calculator will suggest the best bedtimes based on natural 90-minute sleep cycles. Falling asleep at these times helps you wake up refreshed, aligned with your circadian rhythm.
Why Circadian Rhythm Matters
Disruptions to your circadian rhythm — from shift work, jet lag, or irregular sleep schedules — can lead to insomnia, fatigue, mood issues, and reduced cognitive function. Long-term disruption is linked to obesity, diabetes, and cardiovascular disease.
Tips for Supporting a Healthy Circadian Rhythm
- Get morning sunlight to anchor your circadian clock.
- Stick to a consistent sleep schedule, even on weekends.
- Limit blue light exposure (phones, screens) in the evening.
- Align meals and exercise with daylight hours.
Learn More
Your circadian rhythm works hand in hand with the stages of sleep. Explore related guides: