Nutrition Diet: Can I drink liquids if I'm fasting?

October 21, 2025 •

4 min read

Proper hydration is critically important during any fasting regimen, as the body still loses water through normal functions like urination and sweating. Many people wonder, 'Can I drink liquids if I'm fasting?'. While the answer is often a resounding 'yes', the specific types of liquids permitted can vary depending on the fasting method and your personal health goals.

Quick Summary

Fasting rules for liquid intake depend on the specific type of fast being observed. For most intermittent and water fasts, calorie-free beverages like water, black coffee, and herbal tea are permitted. These liquids are essential for staying hydrated, managing hunger, and preventing negative side effects associated with fluid loss during fasting periods.

Key Points

Stay Hydrated: Water is essential and encouraged during most fasts to prevent dehydration and manage hunger.
Check Your Fasting Method: The rules on liquids vary significantly; intermittent and water fasts allow water, while dry fasts do not.
Calorie-Free is Key: Stick to zero-calorie beverages like plain water, black coffee, and unsweetened tea to avoid breaking your fast.
Avoid Sugary Drinks: All caloric beverages, including juice, soda, and milk, trigger an insulin response and will break a fast.
Consider Electrolytes: For longer fasts or intense exercise, consider adding zero-calorie electrolyte supplements to your water to replenish lost minerals.
Consult a Doctor: If you have a health condition or are fasting before a medical procedure, always follow your doctor's specific instructions.

The Importance of Hydration During Fasting

Staying hydrated is one of the most crucial, yet often overlooked, aspects of a successful and safe fast. During a fasting window, the body undergoes several metabolic shifts. As your body depletes its stores of glycogen—the stored form of carbohydrates—it also releases the water molecules bound to it, which can lead to significant fluid loss. A decrease in insulin levels during fasting also causes the kidneys to excrete more sodium and water, further contributing to a natural diuretic effect.

Failing to replenish these lost fluids can result in dehydration, leading to a host of unpleasant symptoms such as headaches, fatigue, dizziness, and muscle cramps. Proper hydration helps maintain blood volume, supports vital organ function, and can even help curb hunger pangs. Water is your best and safest option for hydration, as it contains no calories and does not trigger an insulin response.

Fasting Protocols and Liquid Guidelines

The ability to drink liquids while fasting is highly dependent on the type of fast you are following. It is critical to understand the specific rules for your chosen protocol.

Intermittent Fasting (IF)

For most forms of intermittent fasting (like 16:8 or 5:2), zero-calorie liquids are permitted during the fasting window. The primary goal of these fasts is to keep insulin levels low, and since calorie-free beverages do not trigger an insulin spike, they are allowed.

Water Fasting

This is a more restrictive fast where you consume only water for a set period, typically 24 hours or longer under medical supervision. While only water is permitted, some experts recommend mineralized water to replace lost electrolytes.

Dry Fasting

Dry fasting is the most restrictive form, prohibiting all food and liquids, including water, for a specific duration. This practice carries the highest risk of dehydration and should not be undertaken for extended periods without professional medical guidance. Some religious fasts, such as Ramadan, are a form of dry fasting during daylight hours.

Medical Fasting

Before specific medical procedures or blood tests, a healthcare provider may require fasting for 8-12 hours. In many cases, plain water is the only liquid permitted, but it is vital to follow your doctor's exact instructions.

What Liquids are Allowed During a Fast?

For most health-focused fasts, the following liquids are generally safe and encouraged:

Plain Water: The number one priority. Stay hydrated by sipping consistently throughout your fasting window. Sparkling water is also a great zero-calorie option.
Black Coffee: Unsweetened black coffee is acceptable and contains minimal calories, which won't break a fast. It can also help suppress appetite and boost energy.
Unsweetened Tea: Herbal teas (like peppermint or chamomile), green tea, and black tea are safe options, provided no sugar or milk is added. Green tea, in particular, contains beneficial antioxidants.
Apple Cider Vinegar (ACV): Diluting 1-2 teaspoons of ACV in water is an option for some. It contains minimal calories and is believed to have health benefits.
Bone Broth: For longer fasts, bone broth can help replenish essential electrolytes and minerals. However, since it contains a small number of calories, it may not be suitable for the strictest fasts aimed at maximizing autophagy.

What Liquids to Avoid?

To maintain a true fasted state, you must avoid any beverage with significant caloric or sugar content, as these will trigger an insulin response and negate the benefits of fasting.

Sugary Drinks: This includes regular soda, sweetened tea, fruit juices, and sports drinks.
Dairy: Milk, cream, and other dairy products contain lactose (sugar) and calories that break a fast.
Alcohol: Alcohol contains calories and significantly impacts your metabolism, hindering the benefits of fasting.
Coffee Additives: Flavored syrups, sugar, honey, and most creamers (dairy or non-dairy) will break a fast.
Artificial Sweeteners: The effect of zero-calorie sweeteners is debated. While some claim they don't break a fast, others suggest they might trigger an insulin response or increase cravings. When in doubt, stick to plain water.

Fasting Liquid Intake Comparison


Feature	Intermittent Fasting (IF)	Water Fasting	Dry Fasting
Purpose	Weight loss, metabolic health	Detoxification, metabolic benefits	Religious observance, deep detoxification
Water Allowed?	Yes - Crucial for hydration.	Yes - Only liquid permitted.	No - No liquids or food.
Other Zero-Calorie Liquids?	Yes - Black coffee, unsweetened tea allowed.	No - Water only.	No - Absolute abstinence.
Risks of Dehydration?	Moderate, if hydration is not managed.	High, if duration is not carefully monitored.	Highest, due to no water intake.
Duration	12-36 hour cycles.	Typically up to 24 hours, longer under supervision.	Short, typically daylight hours.

Best Practices for Hydration While Fasting

To ensure your fasting period is both safe and effective, adopt these best practices:

Monitor Your Urine: The color of your urine is a simple indicator of hydration. Aim for a pale yellow to clear color. Dark yellow or amber indicates dehydration.
Sip Consistently: Don't wait until you feel thirsty to drink. Sip water throughout the day to maintain a steady hydration level.
Use Electrolyte Supplements: For longer fasts or if you're exercising, add a pinch of Himalayan pink salt or a zero-calorie electrolyte supplement to your water to replenish essential minerals lost.
Mind Your Caffeine: While black coffee and tea are permitted, excessive caffeine can have a diuretic effect. Moderate your intake and always prioritize water.

Conclusion

For most people practicing intermittent fasting for weight loss or metabolic health, the answer to 'Can I drink liquids if I'm fasting?' is a definitive yes. Plain water is always the safest and most beneficial option, but zero-calorie beverages like black coffee and unsweetened tea can also be included. Understanding the differences between fasting types and sticking to calorie-free, non-insulin-spiking liquids will help you maximize the benefits of your fast while prioritizing your health. As with any significant dietary change, it is always recommended to consult with a healthcare professional before beginning a fasting regimen.

More on fasting guidelines from Johns Hopkins Medicine here.

Frequently Asked Questions

No, drinking plain water does not break a fast. In fact, it is highly recommended to drink water while fasting to stay hydrated and support bodily functions.

Yes, black coffee is generally considered safe to consume during a fast, as it contains minimal calories and won't trigger an insulin response. However, you must drink it black, without any sugar, cream, or milk.

Unsweetened black, green, and herbal teas are all suitable options during a fast. Avoid any teas with added sugars, flavorings, or milk.

The consensus on artificial sweeteners is mixed. Some experts advise avoiding them due to the potential for an insulin response, while others believe they have a minimal impact. For the purest fast, stick to plain, unflavored water.

Bone broth is a debated topic during strict fasts because it contains a small number of calories. However, during longer fasts, many people use it to replenish electrolytes. For shorter fasts, it may be best to avoid.

When fasting, your body releases stored glycogen, which also releases bound water molecules. This, combined with lower insulin levels, leads to greater fluid excretion. Drinking more water prevents dehydration and side effects like headaches.

This is known as dry fasting and is significantly riskier due to the high potential for dehydration. It is not recommended for extended periods and should only be undertaken with extreme caution and medical supervision.

When fasting for a medical test, always follow your doctor's specific instructions. Often, you can drink plain water, but you must avoid all other beverages, including coffee and tea, to prevent skewed results.