FASTLYTEWater fasting timer, any length.
Track multi-day water fasts and your electrolytes — sodium, potassium, magnesium. Every fast length is free. No account, works offline.
Get it on Google PlayFree with ads. Fastlyte Pro removes ads and adds hourly electrolyte charts, fast comparisons, PDF reports, dose reminders, big widgets and themes — yearly, monthly, or once for life. Every fast length was already free.
Every fast length is free
24, 36, 48 or 72 hours, 5 or 7 days, a custom goal or open-ended. The timer counts days and hours and keeps going past your goal. Nothing is locked, ever.
Electrolytes in mg
Save your own doses once — a pinch of salt, a magnesium tablet, your own mix — and log them with one tap. See sodium, potassium, magnesium and water for today and the last 24 hours.
How you feel
Log headache, dizziness, cramps or poor sleep with a severity. Red signs such as fainting or chest pain open a clear “stop and get help” card.
Day-by-day history
Unlimited history of every fast with milligrams per day, water and symptoms side by side. Edit start or end times whenever you need to.
Accurate through restarts
Milestone alerts at 24, 36, 48, 72 hours and beyond, a live notification and a home-screen widget — correct after a reboot, a time-zone change or daylight saving.
No account. No cloud.
Everything stays on your phone and works in airplane mode. Back up to a file you control, optionally encrypted.
Safety first. Fastlyte is a timer and log, not medical advice. Fasting longer than 24 hours can be dangerous — talk to a doctor first, especially if you are pregnant or breastfeeding, under 18, have diabetes, heart or kidney disease, take medication, are underweight or have a history of eating disorders. Electrolyte reference values in the app are general figures for adults from the NIH Office of Dietary Supplements, not advice for fasting.