Fasted FASTED

Water Intake Calculator

Calculate your optimal daily water intake based on your weight, activity level, climate, and fasting status.

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Proper hydration is one of the most overlooked aspects of successful intermittent fasting. Since you are not getting water from food during your fasting window, your fluid needs change and many common fasting complaints like headaches and fatigue are actually signs of dehydration.

Knowing your personal water target — adjusted for your size, activity level, and climate — helps you fast more comfortably and safely. Staying ahead of thirst during fasting hours makes the entire experience significantly easier.

Frequently Asked Questions

Does drinking water break a fast?
No. Plain water contains zero calories and does not trigger an insulin response, so it does not break your fast. In fact, staying well-hydrated during fasting is essential for health, energy, and appetite management. Black coffee and plain tea are also generally accepted.
How much extra water should I drink during fasting?
During fasting, you miss out on water from food (which typically provides 20-30% of daily intake). Aim to drink an additional 2-4 cups beyond your normal target during fasting hours to compensate. Sip consistently throughout your fast rather than drinking large amounts at once.
What are the signs of dehydration during fasting?
Common signs include headaches, dizziness, dark urine, dry mouth, fatigue, and difficulty concentrating. Many symptoms people attribute to fasting hunger are actually dehydration. If you feel unwell during a fast, try drinking a large glass of water before deciding to break it.
What about electrolytes during fasting?
Electrolytes (sodium, potassium, magnesium) are important during extended fasts. For fasts under 24 hours, a balanced diet during your eating window usually suffices. For longer fasts, consider adding a pinch of salt to water or using an electrolyte supplement that contains no calories or sweeteners.

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Log your fasting and hydration habits in Fasted

The Fasted app helps you build consistent fasting habits and reminds you to stay hydrated throughout your fast.

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