Do Liquids Count During Fasting? A Comprehensive Guide

November 24, 2025 •

4 min read

According to a 2025 study, proper hydration is crucial for overall health, but it becomes even more critical during fasting periods. The key question is: do liquids count during fasting? The simple answer is that it depends on the type of liquid and the specific fasting protocol you follow.

Quick Summary

The impact of liquids on a fast is determined by their calorie content and metabolic effect. Calorie-free options like water, black coffee, and unsweetened tea are generally permitted, while caloric beverages and artificial sweeteners can break a fast. Proper hydration supports metabolic function and hunger management during fasting periods.

Key Points

Strict Fasting Rule: Any liquid with calories will break a strict fast, including milks, juices, and sweetened coffees.
Zero-Calorie Liquids Are Safe: Water, plain black coffee, and unsweetened teas are generally accepted and encouraged during fasting.
Hydration is Crucial: It is critical to drink plenty of water while fasting to prevent dehydration, which can cause fatigue and headaches.
Artificial Sweeteners Are Debated: Although calorie-free, some artificial sweeteners may provoke an insulin response, so many fasters choose to avoid them.
Modified Fasting Varies: Some modified fasting protocols, like the 5:2 diet, allow for small, controlled calorie intake during fasting periods.
Exercise and Electrolytes: For longer fasts or during exercise, supplementing with zero-calorie electrolytes may be necessary to maintain mineral balance.
Listen to Your Body: If you feel dizzy, nauseous, or unwell, adjust your liquid intake or break your fast early.

The Importance of Staying Hydrated While Fasting

Staying properly hydrated is one of the most important aspects of any fasting regimen. When you fast, your body still loses fluids through normal processes like sweating and urination. This can be compounded as the body uses stored glycogen for energy, which also releases water. If you do not replenish these lost fluids, you risk dehydration, which can cause headaches, fatigue, dizziness, and decreased metabolism. For those engaging in longer fasts, replacing lost electrolytes is also a vital consideration.

Which Liquids Are Allowed During a Fast?

Not all liquids are created equal when it comes to fasting. The general rule of thumb is to stick to calorie-free or very low-calorie beverages that do not trigger an insulin response.

Fasting-Friendly Liquids

Water: Plain still or sparkling water is the ultimate zero-calorie beverage and is essential for hydration. Add a slice of lemon or cucumber for flavor without breaking your fast.
Black Coffee: Unsweetened, plain black coffee is acceptable and can help suppress appetite due to its caffeine content. However, avoid adding sugar, milk, or other caloric creamers.
Unsweetened Tea: Herbal teas and green or black tea without any added sweeteners are calorie-free and can offer additional health benefits.
Diluted Apple Cider Vinegar: Mixing a small amount (1-2 teaspoons) of apple cider vinegar with water is acceptable and may help curb cravings for some people.

Liquids That Will Break a Fast

Juice: Even freshly squeezed fruit and vegetable juices contain significant sugar and calories that will break your fast.
Sodas and Sweetened Drinks: Any regular soda, sweetened tea, or sports drink is loaded with sugar and will immediately break a fast.
Milks: This includes all types—dairy, almond, oat, and soy. While some may be lower in fat, they all contain calories and protein that will trigger a digestive response.
Alcohol: All alcoholic beverages contain calories and carbs that break a fast and can also lead to dehydration.
Bone Broth: While a great source of electrolytes, bone broth contains protein and calories that will technically break a strict fast. Some modified fasts may permit it for mineral replenishment, but it is not for a true, strict fast.

Comparison of Fasting-Friendly vs. Fast-Breaking Liquids


Aspect	Fasting-Friendly Liquids	Fast-Breaking Liquids
Examples	Water, black coffee, unsweetened tea, diluted ACV	Juices, sodas, milks, alcohol, sweetened coffee/tea
Calorie Content	Minimal to zero calories (under ~5)	Significant calorie content (often 50+ calories)
Metabolic Effect	No significant insulin spike, maintains ketosis	Triggers insulin response, stops fat burning, ends ketosis
Purpose	Hydration, appetite suppression, cellular cleanup (autophagy)	Nutrient delivery, energy provision
Recommended Intake	Liberal consumption encouraged	Forbidden during fasting window (except for specific, modified protocols)
Additives	Should be plain or naturally flavored (e.g., lemon slice)	Often contain added sugars, syrups, and artificial sweeteners

What About Artificial Sweeteners?

This is a gray area that is highly debated. While artificial sweeteners contain zero calories, some research suggests they can still trigger a cephalic-phase insulin response. This means your brain and body can be tricked into releasing insulin in anticipation of sugar, which can interfere with the metabolic goals of fasting. For this reason, many fasting proponents advise avoiding them entirely during a fasting window to be safe. However, the impact is minimal for some individuals, and a non-caloric sweetener might help them stick to their fast by satisfying a craving.

Practical Tips for Managing Liquids During a Fast

Managing your liquid intake effectively can make your fast more comfortable and successful. Here are some tips to help:

Timing Your Beverages

Morning Coffee: If you are a coffee drinker, having it black in the morning can help suppress hunger and boost focus during the initial fasting hours.
Water Throughout the Day: Sip water consistently throughout your fasting window to maintain hydration and manage hunger pangs. Don't wait until you are very thirsty.
Breaks and Exercise: If you are exercising while fasting, consider adding a pinch of salt to your water or using a zero-calorie electrolyte supplement to replenish minerals lost through sweat.
Break Your Fast Mindfully: When it's time to eat, consider breaking your fast with a hydrating food like watermelon or a glass of water to ease your body back into digestion.

Conclusion

Understanding which liquids are acceptable during a fast is essential for maximizing its benefits. For most standard fasting protocols, the simple answer to 'do liquids count during fasting?' is that only zero-calorie drinks like water, plain coffee, and unsweetened tea are truly permissible, as anything with caloric content will break your fast and halt the desired metabolic processes. For those new to fasting or seeking specific health goals, consulting a healthcare professional is always recommended. With a clear understanding of the rules, you can stay hydrated, manage hunger, and successfully achieve your fasting objectives.

Important Outbound Link

For a deeper dive into the science behind intermittent fasting, you can visit the Johns Hopkins Medicine page on the subject: https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work.

Frequently Asked Questions

No, adding milk—whether dairy, almond, or oat—to your coffee introduces calories and protein, which will break your fast and end the metabolic state you are trying to maintain.

No, plain sparkling water without any added sugar or artificial sweeteners is calorie-free and will not break your fast. It is a good way to add variety to your liquid intake.

Bone broth technically contains protein and calories, which will break a strict fast. It is best to avoid it during your fasting window unless you are following a modified protocol that allows for minimal calorie intake.

Plain water is the best liquid to drink while fasting, as it is calorie-free and essential for staying hydrated. Black coffee and unsweetened tea are also excellent options.

The impact of diet sodas and zero-calorie sweeteners on fasting is debated. While they have no calories, some evidence suggests they may trigger an insulin response. To be safe, many fasters avoid them entirely.

The amount of water needed varies by individual, but it's important to drink enough to keep your urine a pale yellow color. A good rule of thumb is to aim for around 8 cups per day, or more, especially if you're exercising.

Generally, yes, as long as you are only infusing the water with small amounts of fruit like lemon or cucumber slices. The amount of calories and sugar that are infused is usually negligible and won't impact your fast.