Caffeine timing is an easy experiment to run on yourself.
Log caffeine in Quick Log, then compare cutoff days with your sleep and recovery. daygauge does not tell you to quit coffee.
Start with what your own data can show.
Most people want the benefit of caffeine without the sleep cost.
The useful question is personal: which cutoff time seems to protect your sleep, on your schedule, against your own baseline?
Log caffeine, or use the Late caffeine chip, in Quick Log. daygauge shows those days beside your sleep timing, sleep duration, HRV and resting heart rate.
What this guide covers.
The useful answer is your cutoff, not a universal rule.
Caffeine timing is easy to test because it is simple to log and the readings that may respond are already in Apple Health: sleep timing, sleep duration, resting heart rate and HRV.
daygauge does not tell you to quit caffeine. It shows whether days with an earlier cutoff sit with different sleep or recovery from your usual, and how many paired days that rests on. Alcohol, travel and late bedtimes can blur the picture, so look at those days too.
Strong signal
Repeated cutoff days, a steady wake time, wearable sleep data and similar weekdays to compare against.
Weak signal
One late coffee, no sleep data, or travel, illness, alcohol or a deadline-heavy evening on the same day.
Useful experiment
Try no caffeine after 14:00 for five weekdays, log it, then compare your sleep timing, duration and HRV with your usual.
Boundary
daygauge gives no advice on pregnancy, medication interactions, anxiety, arrhythmia or other medical situations.
How the app handles this.
What this can look like in the app.
No caffeine after 14:00 logged on 5 days; sleep started 26 minutes earlier than on other weekdays.
ExampleConfidence rises when the same pattern repeats against your own baseline and drops when key signals are missing.
Try one small change, log it, then see whether the pattern repeats over the next week.
Example 1
Late caffeine day: sleep was 41 minutes shorter than your average.
Example 2
Recovery: resting heart rate on cutoff days sat close to your average.
Further reading.
These studies describe groups of people. They help explain the topic, but they cannot tell you what will happen to you.
- Sleep Advances 2023 caffeine dose and timing study
- Sleep Medicine Reviews caffeine and sleep meta-analysis
- Clinical Nutrition ESPEN 2025 review of caffeine and sleep in athletes
Research context only. daygauge does not diagnose, treat, prevent or predict disease risk. Personal medical concerns belong with a qualified clinician.
Caffeine timing and daygauge.
Can daygauge tell me the best time to stop caffeine?
No. You pick a cutoff and log it, and daygauge shows your sleep and recovery on those days next to your other days.
Will one late coffee change my Life Index?
No. Caffeine logs do not change your Life Index. One late coffee is one day, and a pattern needs repeated days.
What if I do shift work?
Compare your own similar days and sleep windows, not a generic bedtime.
Is this medical advice?
No. Caffeine patterns are personal analytics, not clinical guidance.
What daygauge does not do.
Related guides.
Want to test your own caffeine cutoff?
daygauge is free to download. Pro is £8.99 a month or £49.99 a year.
Download on the App StorePersonal analytics, not medical advice