Can I Drink Probiotic Drinks While Fasting?

December 18, 2025 •

4 min read

While fasting for general health benefits, some people choose to take probiotic supplements that contain negligible calories and are unlikely to trigger an insulin response. This leads many to wonder, can I drink probiotic drinks while fasting, or will the calories interfere with the fast?

Quick Summary

Probiotic supplements typically do not break a fast, but many probiotic drinks contain enough calories and sugar to interfere with the fasting state. Choosing low-calorie, sugar-free options is key to supporting gut health without disrupting your fast.

Key Points

Strict Fasting vs. Intermittent Fasting: Your fasting type dictates whether probiotic drinks are acceptable; strict fasts prohibit all calories, while intermittent fasters have more flexibility depending on their goals.
Probiotic Drinks Contain Calories: Most probiotic beverages, including kefir and kombucha, have calories and sugar that will break a fast and halt metabolic processes like autophagy and ketosis.
Probiotic Supplements Are Different: Calorie-free probiotic supplements in capsule or powder form typically do not break a fast and can be taken during your fasting window.
Read All Nutrition Labels Carefully: To avoid accidentally breaking your fast, check for added sugars, juices, and other caloric fillers in any probiotic product you consider.
Optimize Timing for Best Results: For maximum probiotic efficacy during fasting, take supplements on an empty stomach or as directed. Consume probiotic drinks only during your designated eating window.
Probiotics Can Enhance Fasting Benefits: Supporting your gut microbiome with probiotics can help reduce inflammation, improve digestion, and maintain gut health, complementing the benefits of fasting.

What is the goal of your fast?

Determining whether you can drink a probiotic beverage during a fast largely depends on the specific type of fasting you are doing and your health goals. A strict water fast, for example, is broken by consuming any calories, meaning virtually all probiotic drinks are off-limits. For those practicing intermittent fasting (IF) for metabolic health or weight loss, the rules are less rigid, but calorie-rich drinks will still disrupt key benefits like ketosis. Understanding the fundamental purpose of your fast—whether it's for weight loss, gut rest, or triggering cellular repair processes like autophagy—is the first step.

The crucial difference: Drinks vs. Supplements

The main point of confusion comes from conflating calorie-free probiotic supplements with calorie-containing probiotic drinks.

Probiotic Supplements: These usually come in capsules, powders, or tablets and often contain negligible calories. They are generally considered safe to take during a fasting window without breaking the fast, and some experts suggest that a fasted state can even be an optimal time for their absorption.
Probiotic Drinks: This category includes popular options like kombucha, kefir, and yogurt drinks. While beneficial for gut health, they contain varying amounts of sugar and calories that will technically break a fast and halt metabolic processes like ketosis and autophagy.

Comparing popular probiotic drink options


Drink Type	Calorie/Sugar Content	Fasting Impact	Key Considerations
Kefir	Typically 70-100+ calories and 10g+ sugar per serving (milk-based). Water kefir is lower in calories but still contains some.	Breaks a fast due to calories, protein, and sugars.	Should be consumed during your eating window only.
Kombucha	Can range from 30-60+ calories and 8-15g+ sugar per serving.	Breaks a fast due to calories and sugar content.	Best for the eating window. Always check the nutrition label.
Yogurt Drinks	Often high in calories and sugar, some containing 70+ calories and 10g+ sugar per bottle.	Breaks a fast. The dairy protein can also trigger an insulin response.	Stick to your eating window. Consider unsweetened options.
Probiotic Water/Sodas	Can be low-calorie (e.g., 45-50 calories) or sugar-free.	Low-calorie versions may be acceptable for a 'dirty fast,' but still technically break a strict fast. Zero-calorie, zero-sugar versions are best for fasting.	Check ingredients for added sugars like fruit juice or cane sugar.

Benefits of probiotics during a fasting period

While drinking a probiotic beverage might break a strict fast, incorporating the right probiotic can actually be a beneficial strategy. Research shows that fasting can have a positive effect on the gut microbiome by promoting the growth of beneficial bacteria, and supplementing with probiotics can further support this.

Support for the gut microbiome: Fasting provides a 'rest' for your digestive system. Taking a probiotic supplement can help maintain a healthy balance of gut bacteria during this time, which is especially important if dietary changes during your eating window are causing issues.
Reduced inflammation: Some studies have shown that probiotic supplementation, combined with intermittent fasting, can lead to reduced inflammation and better intestinal health.
Improved digestion: For many, reintroducing food after a fast can cause bloating or digestive issues. Having a healthy gut flora, supported by probiotics, can ease this transition and improve overall digestion during your eating window.

Considerations for taking probiotics while fasting

For those determined to maintain a strict fast, the only safe bet is to avoid all probiotic drinks with calories. Instead, opt for a high-quality, calorie-free probiotic supplement.

When to take: The ideal time to take a probiotic supplement can depend on the specific product. Some are most effective on an empty stomach to quickly pass through the stomach's acid, while others are designed to be taken with a small meal. Always follow the product's instructions. A common practice is to take it first thing in the morning or just before breaking your fast.
Choosing a quality supplement: Ensure you select a reputable brand with transparent labeling regarding its ingredients. Avoid gummy vitamins or other supplements with added sugars or fillers that can break your fast.

Breaking your fast with probiotic foods

For intermittent fasting, you can also incorporate probiotic-rich foods like unsweetened yogurt or kefir during your eating window. Breaking a fast gently is important to avoid shocking your digestive system. Fermented foods are excellent for providing your gut with good bacteria and enzymes that assist in digestion.

Conclusion: The final word on probiotic drinks and fasting

Can I drink probiotic drinks while fasting? For strict fasting, the answer is generally no, as most contain calories that will break your fast. For intermittent fasting, it's a matter of weighing your goals. If maintaining a fasted state is the priority, avoid probiotic drinks in favor of water, unsweetened tea, or black coffee. If gut health is a key focus and you are comfortable with a 'dirty fast'—which may involve minimal caloric intake—a very low-calorie probiotic water might be an option, though supplements are the safest bet. The key takeaway is to read all nutrition labels carefully and understand how different probiotic sources impact your specific fasting protocol.

Disclaimer: Always consult a healthcare professional before starting any new dietary or fasting regimen, especially if you have pre-existing health conditions like diabetes.

Key Takeaways

Check the label: Most probiotic drinks contain sugar and calories that will break a fast.
Supplements are safer: Calorie-free probiotic supplements (capsules, powders) are generally safe during a fast.
Timing matters: Take supplements on an empty stomach or as directed to maximize probiotic survival.
Wait for your eating window: Probiotic foods like yogurt or kefir should be consumed during your feeding period.
Define your goals: A 'dirty fast' may permit low-calorie drinks, but a strict fast does not.
Support gut health: Probiotics can be a helpful tool for maintaining gut health, especially for those new to fasting.

Frequently Asked Questions

Yes, a probiotic drink containing sugar and calories will break a fast. Fasting relies on metabolic switches that are triggered by abstaining from caloric intake. The sugar and calories will halt these processes, including ketosis and autophagy.

No, kombucha contains sugar and calories from its fermentation process. Drinking it during your fasting window will break your fast. It should be consumed during your designated eating period.

A 'dirty fast' is when a minimal number of calories (typically under 50) are consumed during the fasting window, which technically breaks the fast but may allow some of the benefits to continue. In this case, a very low-calorie probiotic water or supplement might be acceptable, but it still depends on your specific fasting goals.

The ideal time to take a probiotic supplement is often on an empty stomach, either first thing in the morning or 2-3 hours after your last meal before bed. This allows the beneficial bacteria to pass through the stomach's acidic environment more quickly and reach the intestines.

Yes, they are different. Milk kefir is higher in calories and protein and will definitely break a fast. Water kefir is lower in calories, but still contains some and will technically break a strict fast, though some intermittent fasters may find it acceptable.

Consuming probiotics with calories and sugars can trigger an insulin response and knock you out of ketosis, which is a key metabolic state during fasting. Calorie-free probiotic supplements, however, should not affect ketosis.

No, taking a calorie-free probiotic supplement will not stop autophagy, the body's cellular recycling process. Autophagy is primarily stopped by consuming calories, especially protein and carbohydrates, not by probiotic bacteria themselves.