Mentis- Caffeine has a half-life of roughly 5 hours, longer for some people.
- 400mg of caffeine (about 3–4 cups of coffee) six hours before bed cut sleep by over an hour (Drake et al., 2013).
- Caffeine also makes sleep lighter, even when you fall asleep easily.
- For an 11pm bedtime, a last cup by about 2pm is a good rule.
How does caffeine affect sleep?
Through the day, a chemical called adenosine builds up in your brain and creates sleep pressure, the heavy, sleepy feeling at night. Caffeine blocks adenosine's receptors, so you feel less tired. While it's in your system, it keeps blocking that sleepy signal, including at bedtime.
It also changes the sleep you get. A 2023 meta-analysis in Sleep Medicine Reviews found caffeine shortened total sleep by about 45 minutes, made it take longer to fall asleep and reduced deep sleep. Many people say "coffee doesn't affect me" because they can still fall asleep. The effect shows up as lighter sleep and a groggier morning.
When should I have my last coffee or chai?
Drake's 2013 study gave people caffeine at bedtime, three hours before or six hours before. Even at six hours, sleep was cut by more than an hour. Researchers suggest stopping at least six hours before bed, and longer for big doses. As a simple rule:
- Bed at 11pm: last caffeine by about 2pm.
- Bed at midnight: last caffeine by about 3pm.
- If you're sensitive or sleeping badly: caffeine only before noon for two weeks, and see what changes.
How much caffeine is in chai, coffee and cola?
Amounts vary a lot with the leaf, the brew and the cup size. As a rough guide:
| Drink | Typical caffeine |
|---|---|
| Filter coffee / brewed coffee (one cup) | roughly 80–120mg |
| Espresso (one shot) | roughly 60–75mg |
| Masala chai / black tea (one cup) | roughly 30–60mg |
| Green tea (one cup) | roughly 25–45mg |
| Cola (330ml can) | roughly 30–40mg |
| Energy drink (250ml) | roughly 80mg |
| Chamomile, tulsi, most herbal teas | usually none |
Four small chais through the afternoon can add up to as much as two cups of coffee.
What about the 4pm slump?
The mid-afternoon dip is normal: your body clock has a small sleepiness window in the early afternoon. Instead of a late coffee, try 10 minutes outside in daylight, a short walk, a glass of water or a 15–20 minute nap if you can. The Mentis Sleep plan has a guided audio for this moment: "The 4 PM Slump".
Does alcohol help you sleep?
It can make you drowsy, but it breaks up the second half of the night and reduces dream sleep. That's often why people wake at 3am after drinks. If you drink, keep it light and early, and give it a few hours before bed. The Sleep plan's chapter Nothing borrowed covers caffeine and alcohol together, including "If You Drink: This Week, No Weeknight Drink".
How Mentis helps
The Deep Sleep Reset plan doesn't ask you to give up chai. It helps you move it. The journal "Every Cup, Today" shows how much you really have and when. Then you pick a cut-off and watch what happens to your sleep in your daily check-ins. If you're still struggling after that, try the full sleep schedule reset.
Frequently asked questions
How long before bed should I stop drinking coffee?
At least six hours, and eight is safer for many people. If you go to bed around 11pm, a last cup by about 2 to 3pm protects your sleep.
Does chai keep you awake?
Yes, chai contains caffeine, usually less than coffee. A strong cup of masala chai can still affect sleep if you drink it in the evening, especially if you have several.
Why can I fall asleep after coffee but still feel tired?
Some people can fall asleep with caffeine in their system, but it still makes sleep lighter and reduces deep sleep, so you wake less refreshed.
Does green tea have caffeine?
Yes, green tea has caffeine, typically less than black tea or coffee. Herbal teas like chamomile or tulsi are usually caffeine-free.
- Drake C et al. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med 9(11).
- Gardiner C et al. (2023). The effect of caffeine on subsequent sleep: a systematic review and meta-analysis. Sleep Medicine Reviews 69.
- Clark I & Landolt HP (2017). Coffee, caffeine, and sleep: a systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews 31.
- Ebrahim IO et al. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research 37(4).