Does Fasting Usually Include Water? Understanding Hydration in Different Fasting Protocols

October 24, 2025 •

3 min read

Approximately 20-30% of daily water intake comes from food, making hydration a key concern during periods of reduced or no eating. This leads many to question: does fasting usually include water?

Quick Summary

Most fasting protocols permit water intake to prevent dehydration, which is essential for bodily functions. Specific rules vary across methods like intermittent, water-only, and dry fasting.

Key Points

Hydration is Generally Allowed: Most common fasting methods, including intermittent fasting, permit and even encourage water intake for hydration.
Water Does Not Break a Fast: Since water contains zero calories and doesn't impact insulin levels, it does not interrupt the fasting state.
Dry Fasting is the Exception: Dry fasting is the only major type of fasting that restricts all fluids, including water, and carries significant risks of dehydration.
Water is Crucial for Managing Side Effects: Drinking enough water helps prevent common fasting side effects like headaches, fatigue, and dizziness.
Other Zero-Calorie Drinks Are Often Allowed: In intermittent fasting, black coffee and unsweetened teas are typically acceptable during fasting windows.
Fasting for Medical Procedures Varies: Rules for fasting before surgery or a medical test are specific and must be strictly followed based on a doctor's instructions.

The General Rule: Hydration is Essential

For the vast majority of fasting approaches, drinking water is not only permitted but actively encouraged. Fasting involves restricting caloric intake, not necessarily fluid intake. Water is essential for maintaining bodily functions, and it does not break a fast because it contains no calories and does not trigger an insulin response. In fact, staying well-hydrated is critical to mitigating common side effects of fasting, such as headaches, fatigue, and dizziness.

The Importance of Water During a Fast

When you fast, your body undergoes several metabolic changes that affect your fluid balance. During the initial stages, as your body depletes its glycogen stores for energy, it also releases the water molecules bound to that glycogen. This can lead to increased urination and a higher risk of dehydration if you don't actively replenish fluids. Water helps with metabolism, waste removal, and can even assist in suppressing hunger pangs.

Fasting Protocols and Their Water Rules

Different fasting methods have distinct guidelines regarding water and other liquids. Understanding these variations is key to a safe and effective fasting experience.

Intermittent Fasting (IF)

This popular method cycles between periods of eating and fasting, such as the 16:8 schedule (16 hours of fasting, 8 hours of eating). During the fasting window, zero-calorie beverages are typically permitted.

Allowed liquids: Water (plain, sparkling, or flavored without calories), black coffee, and unsweetened tea.
Prohibited liquids: Any beverage with calories or sweeteners, such as soda, fruit juice, or coffee with milk and sugar, will break the fast.

Water Fasting

This is a more restrictive protocol where you consume only water for a specific duration, usually 24 to 72 hours. It is important to note that this should not be done for prolonged periods without medical supervision, as it carries risks of electrolyte imbalance and other health complications. Mineralized water is often recommended to help replace lost electrolytes.

Dry Fasting

Dry fasting is the one major exception where all liquid intake, including water, is strictly prohibited during the fasting period. This is a more extreme form of fasting, often practiced for religious reasons, such as during Ramadan, where fasting occurs from dawn to sunset. Dry fasting is more challenging and carries a higher risk of dehydration compared to water fasting. Due to the significant risks, it is typically performed for short periods.

Fasting for Medical Procedures

When preparing for a medical procedure, a fast is often required to ensure an empty stomach. For some procedures, clear liquids like water may be permitted up to a few hours beforehand. However, it is crucial to follow the specific, detailed instructions provided by your healthcare provider, as they can vary depending on the procedure.

Comparison of Fasting Methods and Water Consumption


Fasting Method	Water Allowed?	Other Zero-Calorie Liquids?	Key Consideration
Intermittent Fasting	Yes, highly recommended.	Yes, black coffee, unsweetened tea.	Hydration is crucial for managing hunger and fatigue.
Water Fasting	Yes, it is the only thing consumed.	No.	Risk of electrolyte imbalance and requires careful monitoring.
Dry Fasting	No, all fluid is restricted.	No.	Highest risk of dehydration; typically done for short, specific periods.
Medical Fasting	Depends on the procedure.	Varies, follow specific medical advice.	Strictly adhere to your doctor's instructions for safety.

What to Drink During a Fast (Besides Water)

For intermittent fasting, expanding your beverage choices beyond plain water can help with compliance and hydration. Always opt for options without added sugar or calories.

Black coffee: Contains very few calories and can help suppress appetite.
Unsweetened tea: Herbal or green tea offers a calorie-free, hydrating option.
Flavored or sparkling water: These are acceptable as long as they contain no sugar or calories.
Lemon water: A small amount of lemon juice is generally fine and can add flavor without breaking the fast.
Bone broth: While containing some calories, it is sometimes used during longer fasts to replenish electrolytes.

Conclusion

In summary, the answer to "does fasting usually include water?" is a resounding "yes" for most common fasting practices. For intermittent and water-only fasting, staying hydrated with water and other zero-calorie liquids is a cornerstone of the process, preventing dehydration and supporting metabolic functions. The only significant exception is dry fasting, which excludes all fluids. Regardless of your fasting method, listen to your body and consult a healthcare professional, especially when starting a new protocol, to ensure your safety and success. Johns Hopkins Medicine offers comprehensive resources on intermittent fasting and its benefits.

Frequently Asked Questions

No, fasting without water (dry fasting) is not safe for most people for extended periods due to the high risk of dehydration. It is often done for religious reasons and for very short durations.

There is no single rule, but it is important to drink enough to prevent dehydration. A good guideline is to increase your water intake from a baseline level, listening to your body's thirst signals. Your urine should remain light yellow or clear.

No, black coffee is generally acceptable during intermittent fasting because it contains virtually no calories. However, adding milk, cream, or sugar will break the fast.

Yes, sparkling water without any added calories or sweeteners is fine to drink during a fast.

The key difference is the allowance of water. In water fasting, only water is consumed, while in dry fasting, all liquids and food are restricted.

Yes, drinking water can help reduce hunger pangs. Sometimes, the body mistakes thirst for hunger, and filling your stomach with water can create a sense of fullness.

Yes, prolonged water fasts (longer than 72 hours) carry risks such as electrolyte imbalances, nutrient deficiencies, and muscle loss. They should only be undertaken with professional medical supervision.