FitRest tracks every coffee, tea and energy drink against a daily limit you choose, then estimates how much caffeine is still in your system. It tells you when alertness should peak and when your caffeine level should be low enough for good sleep, so you can time your last cup.
Logging starts from a drink library grouped into Coffees, Teas and Others. If your usual order is not there, create it under My Drinks with a name, a caffeine amount in mg, an icon and a strength from Light to Very Strong. Your own drinks sync to your Apple Watch, which also has 17 preset drinks.
Once a drink is logged, FitRest does more than add up milligrams. It estimates how your caffeine level rises and falls through the day and turns that into a few plain answers.
Caffeine works by blocking adenosine, the chemical that builds up while you are awake and makes you feel sleepy. That is why it sharpens focus, and also why it can keep you up: it takes the body several hours to clear it, so an afternoon coffee can still be active at bedtime. Even when you fall asleep without trouble, caffeine late in the day is widely linked to lighter, less refreshing sleep.
Total amount matters too. General guidance for healthy adults is often given as up to about 400 mg a day, and sensitivity varies a lot between people. The total that suits you is your call, which is why the daily limit in FitRest is adjustable, starting from a Recommended setting.
The Today's Caffeine card on the Dashboard shows your total with a sleep status line underneath, for example "Sleep-safe by 9:40 PM", "Cutoff in 25m", "Cutoff passed" or "You're sleep-safe". It is a quick check before you order another coffee.
Tap any drink in the day's list for its own detail: when its effect peaks, how much of it is still circulating, and how it fits into your system right now. A single large serving is flagged as a High single dose. As you approach your limit, FitRest shows Approaching daily limit, and then You've reached the daily limit.
Caffeine also feeds into Heart Signals on the Heart tab. Its Caffeine & Your HRV view compares your overnight HRV on lighter and heavier caffeine days, so you can see whether your own nights look different after a big caffeine day.
Caffeine logged in FitRest can be saved to Apple Health, and caffeine other apps save there shows up in your timeline tagged External. The Caffeine complication on Apple Watch shows today's total and opens the log page with a tap, and there are Daily and Weekly caffeine widgets for the iPhone Home Screen.
General guidance for healthy adults is often around 400 mg a day, but sensitivity varies. FitRest starts with a Recommended limit and lets you set your own anywhere from 25 to 1,000 mg.
Caffeine is cleared gradually over several hours, which is why an afternoon coffee can still be active at night. FitRest estimates how much is still in your system right now and when you should be sleep-safe.
It depends on your bedtime and how much you have had. FitRest's Sleep Safe time shows when your caffeine level should be low enough for quality sleep, and you can set a Caffeine Cutoff with a warning if you log after it.
Yes. My Drinks lets you create custom drinks with a name, caffeine amount, icon and strength, and they sync to your Apple Watch.
Yes. The watch app's Caffeine page has 17 preset drinks plus your My Drinks and a time picker, and the Caffeine complication opens it with a tap.
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FitRest reads the data already in Apple Health, so there is nothing to set up beyond granting access.
iPhone, iPad and Apple Watch. Requires iOS 17 or later.