Is low-sugar kombucha okay while fasting?

It still has some sugar and calories, so it breaks a strict fast.

Does kombucha break ketosis?

It can, depending on how much sugar remains.

When should I drink kombucha if I fast?

During your eating window, where its calories and probiotics fit best.

Does Kombucha Break a Fast?

Reviewed by the FastTrack team · Updated June 2026

Short answer: Yes

Kombucha breaks a fast. Even low-sugar kombucha contains residual sugar and calories from fermentation, enough to raise insulin and end a fast.

Calories	~30-60 kcal per cup
Breaks a weight-loss fast?	Yes
Breaks ketosis?	Partial
Breaks autophagy?	Yes
Insulin impact	Yes

Why kombucha breaks a fast

Kombucha is fermented sweet tea, and although fermentation consumes some of the sugar, a typical bottle still has 2 to 8 grams of sugar and 30 to 60 calories. That residual sugar provides calories and an insulin response, so kombucha breaks a fast even when it is labeled low sugar.

Save it for your eating window

The probiotics in kombucha are best appreciated during your eating window, where its calories do not matter. If you want a fizzy, flavorful drink during a fast, plain or naturally flavored sparkling water gives you that without the sugar.

How much is safe

Even low-sugar kombucha breaks a strict fast; have it in your eating window instead.

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Frequently asked questions

Does kombucha break a fast?: Yes, the residual sugar and calories break a fast.
Is low-sugar kombucha okay while fasting?: It still has some sugar and calories, so it breaks a strict fast.
Does kombucha break ketosis?: It can, depending on how much sugar remains.
When should I drink kombucha if I fast?: During your eating window, where its calories and probiotics fit best.