Does Yakult break a fast?

Yes. A small bottle has around 50 calories, most of it sugar.

Should I take probiotics on an empty stomach?

It depends on the product. Some are designed for an empty stomach, others for meals; follow the label.

Do probiotic gummies break a fast?

Yes in the strict sense, with a few grams of sugar per gummy. Capsules are the fasting-friendly form.

Does kefir break a fast?

Yes. Kefir is fermented milk with protein, fat and milk sugar.

Do Probiotics Break a Fast? It Depends

Reviewed by the FastTrack team · Updated June 2026

Short answer: It depends

Probiotic capsules do not break a fast: they have almost no calories. Probiotic gummies, yogurt drinks and kombucha are different, since they carry sugar or milk. A small bottle of a yogurt-style probiotic drink has around 50 calories and about 10 g of sugar.

Calories	~0 kcal (capsule), ~50 kcal (yogurt drink)
Breaks a weight-loss fast?	No
Breaks ketosis?	No
Breaks autophagy?	Unlikely
Insulin impact	None for capsules

Why a capsule keeps you fasted

A probiotic capsule holds a powder of live bacteria and a little filler, far below anything that could raise insulin or end a fast. Taking it during the fasting window is fine for any fasting goal.

The food-based versions

Yogurt drinks, kefir and probiotic shots bring milk sugar or added sugar, and gummies are candy with bacteria in them. Some capsules are labeled to be taken with food, which can help the bacteria survive stomach acid; follow the label.

How much is safe

One capsule a day, at the time your label recommends. Keep yogurt drinks, kefir and gummies for your eating window.

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Frequently asked questions

Does Yakult break a fast?: Yes. A small bottle has around 50 calories, most of it sugar.
Should I take probiotics on an empty stomach?: It depends on the product. Some are designed for an empty stomach, others for meals; follow the label.
Do probiotic gummies break a fast?: Yes in the strict sense, with a few grams of sugar per gummy. Capsules are the fasting-friendly form.
Does kefir break a fast?: Yes. Kefir is fermented milk with protein, fat and milk sugar.