Name: HalfLife Caffeine
Rating: 5 (1 reviews)
Author: JanMesarc

Know your caffeine. Sleep better.

HalfLife Caffeine is a free, science-based caffeine tracker for your Garmin watch. It models how caffeine decays in your bloodstream using a pharmacokinetic half-life 5.7 hours by default, and adjustable to your own metabolism, so you always know how much is still active, and when you'll be safe to sleep.

Features

At-a-glance tracking. See current caffeine level and time to sleep-safe right in the widget loop.

Full-screen detail views
- Summary: current level, daily intake vs. limit, time to sleep-safe
- Timeline: 12-hour graph showing the last 4 hours of history and the next 8 hours of projected decay, with dose markers
- Today's drinks: interactive log with edit-time and delete on each entry — fix a mis-tap or a forgot-to-log-promptly in seconds
- History: 14-day bar chart with day-list drill-down (per-drink detail for recent days, daily totals going back 90 days)

Personalize the model: Set your own caffeine half-life (3–10 hours). Smoking, genetics, pregnancy, and some medications all change how fast you clear caffeine, tune the decay to match you.

Choose your look: Navy or Black background theme. Black is sharper on non-AMOLED (MIP) watches and easier on the battery on AMOLED displays.

12 drink presets included: Espresso, Americano, Drip Coffee (S/L), Latte, Green Tea, Black Tea, Red Bull, Monster, Cola, Dark Chocolate, Pre-Workout.

Add, rename, and remove from the phone companion.

Smart alerts
- Warning at 80% of your daily limit
- Alert when you hit your limit
- Notification when caffeine drops low enough for sleep (within 2 hours of bedtime)

Phone companion: Manage drink presets, adjust limits, view history, see weekly trends, and track your peak caffeine hours, all inside the Garmin Connect app. Watch-side edits and deletes sync automatically.

Your data stays with you. Everything is stored on your watch and phone. No accounts, no cloud, no tracking.

100% free. No ads. No in-app purchases.

Compatibility

42 watches across these families:
- Vivoactive 4, 5, 6
- Venu 2, 2 Plus, 2s, 3, 3s · Venu Sq 2, 2m
- Forerunner 165 (+ music), 255 (+ music, s, sm), 265, 265s, 955, 965
- Fenix 6, 6s, 6 Pro, 6x Pro, 7, 7s, 7x · Fenix 7 Pro family · Fenix 8 (43mm, 47mm, Solar 47mm/51mm, Pro 47mm) · Fenix E
- Epix 2 · Epix 2 Pro (42mm, 47mm, 51mm)