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Fasting Phases

See which fasting phase you’re in from hours fasted.

Not medical advice. Do not use if pregnant, breastfeeding, under 18, history of eating disorder, underweight, type 1 diabetes, or a doctor told you not to fast. Stop for dizziness, fainting, confusion, or rapid heartbeat. Water + electrolytes.
12h 16h 18h 24h
0:00:00
Ready
Not fasting

Start a fast to see your phase.

Presets mark a check-in time. They are not a medical protocol.

What people usually feel

Start the timer to see a commonly described phase.

What to do

Water is fine. Stop if you feel dizzy, faint, confused, or your heartbeat races.

Compare electrolytes and fasting-window aids via your affiliate partners here.

Timeline

    Related

    TDEE Calculator

    Daily calories to maintain, lose, or gain.
    Calorie Calculator

    Targets from your stats and goal.
    Macro Calculator

    Protein, carbs, and fat targets.

    Safety

    This tracker is educational. It is not medical advice and does not diagnose, treat, or tell you to fast.

    Do not use if you are pregnant, breastfeeding, under 18, have a history of eating disorder, are underweight, have type 1 diabetes, or a doctor has told you not to fast.

    Stop immediately for dizziness, fainting, confusion, or a rapid heartbeat. Drink water. Electrolytes are often used during longer windows. Extended fasts (especially past 36 hours) need a clinician — this app will not encourage going longer.

    Related: TDEE · Calorie · Macros

    FAQ

    How does this show my fasting phase?
    Start a timer or enter hours already fasted (or a start time). The app maps elapsed time to commonly described windows — fed, post-absorptive, early fasting, a fat-burning window, and longer stretches. These are educational labels often used in fasting guides, not lab measurements or medical advice.
    Who should not fast or use this tracker?
    Do not use it if you are pregnant, breastfeeding, under 18, have a history of eating disorder, are underweight, have type 1 diabetes, or a doctor has told you not to fast. Stop immediately for dizziness, fainting, confusion, or a rapid heartbeat. Drink water and consider electrolytes. This is not medical advice.
    Can I install Fasting Phases on my phone?
    Yes. On many Android browsers, tap Install App when it appears. On iPhone, open Share, then Add to Home Screen. The page is a standalone PWA and can work offline for /fasting.

    Educational fasting-phase labels. Not medical advice.