What to drink when fasting for 72 hours?: The ultimate guide to safe hydration

October 15, 2025 •

6 min read

Scientific studies show that during an extended 72-hour fast, the body enters a profound state of cellular renewal known as autophagy, which is highly dependent on proper hydration to function optimally. Understanding what to drink when fasting for 72 hours is crucial for maximizing benefits and preventing dehydration.

Quick Summary

Safe liquids for a 72-hour fast include plain water, mineral water, unsweetened black coffee, herbal tea, and calorie-free electrolytes. Prioritizing hydration and replenishing mineral balance is vital to manage symptoms like headaches and fatigue. Avoid all calorie-containing drinks to sustain the fasted state.

Key Points

Water is the foundation: Drink 3-3.5 liters of plain, mineral, or sparkling water daily, as your body requires more fluid intake during a fast.
Electrolytes are crucial after 48 hours: For longer fasts, supplement with pure, zero-calorie electrolyte salts (sodium, potassium, magnesium) to prevent dehydration and mineral imbalance symptoms.
Black coffee is permitted, unsweetened: Use black coffee in moderation to help with energy and hunger, but avoid all additives like sugar, milk, or cream.
Unsweetened herbal tea is a safe option: Herbal teas like chamomile or ginger are calorie-free and can help curb hunger and provide a soothing effect.
Avoid calorie-containing liquids: Any drink with sugar, milk, or significant calories, including bone broth and juice, will break your fast and should be avoided.
Listen for warning signs: Monitor for symptoms like headaches, dizziness, or muscle cramps, which indicate a need for electrolytes or to safely break the fast.

The Importance of Hydration and Electrolytes During Extended Fasting

When undertaking an extended fast, such as for 72 hours, your body undergoes significant metabolic changes. As insulin levels drop, your kidneys excrete more sodium and water, a natural diuretic effect that can lead to rapid fluid loss. Since you are no longer receiving fluids from food, the risk of dehydration and electrolyte imbalance increases dramatically. Staying properly hydrated with the right liquids is the most important aspect of a safe and effective prolonged fast.

Electrolytes—essential minerals like sodium, potassium, and magnesium—are responsible for regulating nerve and muscle function, maintaining fluid balance, and supporting heart health. During a 72-hour fast, your body depletes its stores of these minerals, which can cause unpleasant side effects such as headaches, muscle cramps, and dizziness. Supplementing with the correct type of electrolytes becomes critical to sustain proper bodily functions.

Approved Beverages for a 72-Hour Fast

Plain Water (Still, Mineral, or Sparkling)

Plain water is the most fundamental beverage during a fast and is absolutely essential. Aim for 3 to 3.5 liters per day to compensate for the fluid you would normally get from food. While regular tap water is acceptable, mineral water or sparkling water (with no added sweeteners) can provide a small amount of electrolytes.

Best practices for drinking water:

Drink water consistently throughout the day rather than large amounts at once.
If using tap water, consider adding a pinch of sea salt for basic electrolytes.
Sparkling water can help with feelings of fullness for some people.

Unsweetened Black Coffee

For many, black coffee is a valuable tool during a fast. It can help suppress appetite and provide a mental energy boost due to its caffeine content. Black coffee contains negligible calories and does not trigger an insulin response, making it compatible with a fast.

Tips for consuming black coffee:

Drink in moderation (1–3 cups per day) to avoid jitters or stomach acidity.
Do not add any milk, cream, sugar, or flavored syrups, as these will break your fast.
If sensitive to caffeine, opt for decaf black coffee.

Plain Herbal and Green Tea

Unsweetened tea is another excellent zero-calorie option. Herbal teas like peppermint or chamomile are caffeine-free and can be calming, while green tea offers antioxidants and a mild caffeine boost.

To prepare fasting-friendly tea:

Brew with hot water and drink plain.
Avoid adding any sweeteners, honey, or milk.
For a true "clean fast" focused on autophagy, some experts advise sticking to plain water, but for most, unsweetened tea is acceptable.

Electrolyte Solutions (Zero-Calorie)

Given the significant electrolyte loss during a 72-hour fast, supplementation is often recommended, especially after the first 24-48 hours. This helps prevent the "keto flu" symptoms often associated with extended fasts. The key is to choose a pure, zero-calorie blend without any sugar or artificial sweeteners.

Creating a homemade electrolyte drink:

Mix 1/4 teaspoon of high-quality salt (like Himalayan or Celtic sea salt) into a liter of water. Some add a tiny amount of potassium chloride and magnesium citrate powder.
Alternatively, purchase a reputable, sugar-free electrolyte supplement designed for fasting.

What to Avoid: Drinks That Break Your Fast

Any beverage that contains calories, sugar, or other additives should be avoided during a 72-hour fast. This includes, but is not limited to:

Bone Broth: While nutrient-dense and excellent for breaking a fast, it contains calories and protein, which will interrupt the fasted state.
Sugary Drinks: Soda, juices, and sweetened teas trigger an insulin response and negate the benefits of fasting.
Milks and Creamers: Any form of dairy, including plant-based milks, contains calories and protein.
Alcohol: High in calories and dehydrating, alcohol should be strictly avoided.
Diet Soda and Artificial Sweeteners: The impact of artificial sweeteners on insulin and gut health during a fast is debated. Some studies suggest they can trigger an anticipatory insulin response, making them a risky choice for a strict fast.
Fruit-Infused Water (Except Sparse Lemon/Lime): Infusing water with fruit releases natural sugars, potentially impacting blood sugar and insulin levels. A small squeeze of lemon or lime is often tolerated, but for a true clean fast, it's best to stick to water.

Comparison of Drinks for a 72-Hour Fast


Drink Type	Fasting Compatibility	Key Consideration	Benefits	Notes
Plain Water	Fully Compatible	Essential for hydration	Prevents dehydration, lubricates joints	The baseline for all fasting.
Mineral/Sparkling Water	Fully Compatible	Check for added sugar/flavors	Contains trace minerals, can aid satiety	Natural minerals are a bonus.
Black Coffee	Generally Compatible	Avoid all additives	Suppresses appetite, boosts energy and focus	Limit intake to avoid side effects.
Unsweetened Tea	Generally Compatible	Stick to herbal or plain	Provides antioxidants, can be calming	Ensure no added sweeteners or cream.
Pure Electrolytes	Fully Compatible	Must be calorie/sugar-free	Prevents electrolyte imbalances, reduces fatigue	Necessary for most fasts over 48 hours.
Bone Broth	Breaks Fast	Contains calories and protein	Excellent for refeeding, not for fasting	Should only be consumed when breaking the fast.
Diet Soda	Not Recommended	Artificial sweeteners debated	None for a clean fast	May trigger insulin response, best to avoid.
Fruit Juice	Breaks Fast	High in sugar and calories	None during fasting	Triggers strong insulin response, ending fast.

Conclusion: Prioritizing Safe Hydration

When undertaking a 72-hour fast, what you choose to drink is as important as what you choose not to eat. Safe, non-caloric fluids are the foundation of a successful and comfortable fast. By sticking to plain water, unsweetened teas, black coffee, and pure electrolytes, you can support your body's natural metabolic processes while minimizing common side effects like headaches and fatigue. However, it's crucial to consult a healthcare professional before starting any prolonged fast, especially if you have pre-existing health conditions. Listen to your body and be prepared to end the fast if severe symptoms occur.

For more information on the metabolic processes during fasting, visit the Johns Hopkins Medicine website for detailed research on the body's response.

Essential Safety Reminders

Medical Supervision is Key: A 72-hour fast can be intense. Consult a doctor, especially if you have pre-existing conditions like diabetes, kidney problems, or are on medication.
Proper Refeeding is Crucial: Breaking a 72-hour fast requires a slow, gentle approach, starting with light, easily digestible foods like broth to avoid overwhelming your digestive system.
Exercise Cautiously: Avoid strenuous exercise during a prolonged fast to prevent excessive electrolyte loss and dehydration. Light activity, like walking, is generally fine.

The Power of the Fasting State

Autophagy and Cellular Health: Fasting for 72 hours allows your body to maximize autophagy, a process where damaged cells are broken down and recycled, promoting cellular repair and longevity.
Metabolic Switch to Ketosis: After depleting its glycogen stores, the body switches to burning fat for fuel, entering a state of ketosis that enhances fat loss and provides a cleaner, more efficient energy source.
Improved Insulin Sensitivity: Extended fasting gives your body a break from constantly processing sugar, which can lead to a significant improvement in insulin sensitivity over time.
Enhanced Mental Clarity: Many individuals report experiencing a boost in cognitive function, focus, and memory as the brain shifts to using ketones for energy.
Reduced Inflammation: The fasting state has been shown to reduce markers of chronic inflammation, which is beneficial for various health conditions.

Listen to Your Body

Stay in Tune: If you experience severe symptoms like dizziness, persistent nausea, or heart palpitations, it's important to stop the fast and seek medical advice.
Don't Overdo It: While a 72-hour fast offers profound benefits, longer fasts can be dangerous without proper medical supervision and preparation.

Hydration Is Not Just for Thirst

Avoid Dehydration: On an extended fast, your body loses fluids and electrolytes more rapidly. Ignoring thirst and not drinking enough can lead to severe dehydration.
Support Detoxification: Water is essential for flushing out toxins and metabolic waste that accumulate during fasting and autophagy.

Practical Tips

Prepare in Advance: Before a 72-hour fast, prepare by reducing meal sizes and cutting out processed foods in the days leading up to it.
Have Electrolyte Mix Ready: Purchase or prepare a zero-calorie electrolyte mix in advance so it is ready when you need it, typically on day two.

The Psychology of Fasting

Overcoming Hunger Pangs: A cup of black coffee or herbal tea can be a helpful tool for managing initial hunger pangs, especially during the first 48 hours.
Building Willpower: Successfully completing an extended fast can significantly boost mental resilience and control over cravings, contributing to healthier habits long-term.

The Right Beverages for Your Goals

For Autophagy: Stick strictly to plain water and unsweetened herbal teas. Some purists even avoid coffee to maximize the cellular cleansing process.
For Fat Loss: Black coffee can be a powerful ally by suppressing appetite and boosting metabolism, complementing the shift to fat-burning ketosis.

Frequently Asked Questions

Yes, bone broth contains calories and proteins that will interrupt a true 72-hour fast. It is, however, an excellent source of nutrients and electrolytes and is highly recommended for safely breaking a fast.

The consensus on artificial sweeteners is mixed. Some experts advise avoiding them as they may trigger an insulin response or affect gut health, which could disrupt the fasted state. For a strict 'clean' fast, it's best to avoid all sweeteners.

It is generally recommended to increase your water intake to approximately 3 to 3.5 liters per day. You get less water from food while fasting, and your body needs extra for metabolic processes.

No, adding a pinch of pure salt, such as Himalayan or Celtic sea salt, to your water will not break your fast. It provides crucial sodium, helping to maintain electrolyte balance and is a common practice during extended fasts.

No, bulletproof coffee contains calories from added fats (butter, MCT oil) and will technically break your fast, even if it doesn't cause a significant insulin spike. Stick to plain black coffee for the full benefits of a clean fast.

Symptoms of electrolyte imbalance can include fatigue, dizziness, headaches, nausea, and muscle cramps. If you experience these, it's time to replenish electrolytes with a calorie-free supplement or a homemade solution.

For a 72-hour fast, it is often sufficient to begin electrolyte supplementation after the first 24 to 48 hours, especially if you are active or in a hot climate. Your body's stored electrolytes will be mostly depleted by then.