Why is Kombucha so High in Carbs? The Science of Fermentation and Residual Sugars

December 5, 2025 •

4 min read

While celebrated as a health elixir, kombucha starts its life as a very sugary tea mixture, a crucial ingredient for fermentation. This initial high sugar content is precisely why kombucha is so high in carbs before the SCOBY gets to work, but the final carb count depends heavily on the brewing process.

Quick Summary

Kombucha's carb content originates from the sugar that fuels its fermentation. The final amount is determined by brewing time, temperature, and added flavorings.

Key Points

Essential Fuel: Sugar is a necessary ingredient to feed the SCOBY, and is required for the fermentation process that creates kombucha.
Fermentation Time Matters: The longer kombucha ferments, the more sugar is consumed by the SCOBY, resulting in a lower carbohydrate count in the final beverage.
Flavoring Adds Carbs: Many commercially flavored kombuchas add fruit juices and other sweeteners during secondary fermentation, which significantly increases the carb and sugar content.
Check the Label: To find a lower-carb kombucha, it is essential to read the nutrition label and compare the total sugar content across brands and flavors.
Homemade Advantage: Brewing kombucha at home gives you complete control over fermentation time and flavoring, allowing you to produce a beverage with minimal residual carbs.
Low-Carb Alternatives Exist: Some brands use non-caloric sweeteners or rely on longer fermentation to create low-sugar or zero-sugar kombucha options.
Comparison with Other Drinks: Despite its initial sugar content, many kombuchas contain fewer carbs and sugars than sodas or fruit juices.

Understanding the Essential Role of Sugar

To grasp why kombucha can be high in carbs, one must first understand its foundational ingredient and the fermentation process it undergoes. Kombucha is made by introducing a Symbiotic Culture Of Bacteria and Yeast (SCOBY) to a sweetened tea base. The yeast and bacteria in the SCOBY are what turn this sweetened tea into the tangy, probiotic-rich beverage we know and love. Without sugar, the SCOBY would have no fuel, and the fermentation process would not occur.

Initially, kombucha brew contains a considerable amount of sugar to feed the SCOBY. A typical home-brewed batch might use one cup of sugar for a gallon of tea. During the first fermentation, the yeast consumes the sugar (specifically, sucrose, breaking it down into glucose and fructose) and converts it into alcohol and carbon dioxide, which gives kombucha its fizz. Subsequently, the bacteria then consume the alcohol and some of the remaining sugar, converting it into beneficial organic acids like acetic acid.

Factors Influencing Kombucha's Carb Count

The total carbohydrate content in the final kombucha is not a fixed number; it can vary significantly depending on several key factors:

Fermentation Time and Temperature

The most important variable in controlling carb content is the duration of the fermentation process. The longer the tea is allowed to ferment, the more sugar the SCOBY consumes. As the fermentation progresses, the flavor shifts from sweet to tart and vinegary. A short fermentation leaves more residual sugar and results in a sweeter kombucha, while a longer, more complete fermentation produces a drier, more acidic beverage with fewer carbs. Fermentation temperature also plays a role, with warmer conditions typically leading to a faster and more thorough conversion of sugars.

Flavoring and Secondary Fermentation

Many kombucha brands undergo a second fermentation to add flavor and boost carbonation. During this stage, fruits, fruit juices, or other sugary additions are introduced. While this creates a more palatable, flavorful drink, it also re-introduces sugar and, therefore, more carbohydrates into the final product. Even if the initial fermentation was lengthy, adding a significant amount of fruit juice can negate the carb reduction. This is why brands often have different carb counts depending on the flavor.

Commercial vs. Homemade Kombucha

There's a notable difference in control over carb content between store-bought and homemade brews. Commercial kombuchas are often formulated to appeal to a wider audience, which means a careful balance of sweet and tart is struck. This often leaves more residual sugar than a more aggressive home fermenter might allow. Store-bought brands also contain added sugars for flavoring after pasteurization, which can increase the carb count. Homebrewers, conversely, have complete control. They can let the fermentation run longer to reduce sugar and can use non-caloric sweeteners or low-sugar fruit extracts for secondary fermentation.

The Impact of Added Sugars

Many brands add extra sweeteners after the main fermentation to achieve a consistent taste profile. This might involve cane sugar, fruit concentrates, or other sugary syrups. Consumers should always check nutrition labels carefully to see the total and added sugar content. Some brands now offer low-sugar or zero-sugar options, but these often rely on non-fermentable sweeteners and may not contain the same living cultures as a traditionally fermented brew.

How Kombucha's Carbs Compare to Other Beverages

When you look at the big picture, kombucha is often not as carb-heavy as many other popular drinks, despite its initial sugar content.


Beverage (approx. 8 oz)	Approx. Sugar (g)	Approx. Carbohydrates (g)
Kombucha	3–12	7–12
Orange Juice	24	24
Coca-Cola	22	22
Lemonade	27	27

Conclusion

So, why is kombucha so high in carbs? The short answer is the sugar required to feed the SCOBY during fermentation and the additional sugars used for flavoring. The longer, more complex answer reveals that the final carbohydrate level is highly variable and directly impacted by fermentation duration, temperature, and added flavorings. For those monitoring carb intake, choosing brands with lower sugar counts, opting for unflavored varieties, or brewing at home provides the greatest control over the final product. By understanding the science behind the brew, you can make an informed decision about how kombucha fits into your dietary goals. To learn more about how fermentation benefits your body, consider exploring sources like Healthline: Type 2 Diabetes: Kombucha Tea May Help Reduce Blood Sugar Levels.

The Role of Sugar and Carbs in Kombucha

Sugar as Fuel: Kombucha is high in carbs because it begins as sweet tea, providing the necessary fuel for the SCOBY's fermentation process.
Carb Reduction: As fermentation progresses, the SCOBY consumes the sugar, naturally lowering the total carbohydrate content over time.
Residual Sugars: The final carb count, often appearing high on nutrition labels, is based on the residual sugars left after fermentation.
Secondary Fermentation Impact: Adding fruit juice or other flavorings during secondary fermentation re-introduces sugar, which can increase the overall carb count.
Variable Content: The carb level in kombucha is not uniform; it varies significantly between brands, flavors, and how long the tea is fermented.
Low-Carb Options: Longer home fermentation and choosing unsweetened or low-sugar commercial varieties are ways to reduce carb intake from kombucha.

Frequently Asked Questions

Not necessarily. While kombucha contains sugar, its probiotics and acetic acid may have benefits for blood sugar management. However, diabetics should opt for low-sugar varieties, read labels carefully, and monitor blood glucose levels after consumption.

It depends on the brand and the amount consumed. Some commercially available kombuchas have a carb count that is too high for a keto diet. However, many low-carb and long-fermented homemade kombuchas can be keto-friendly.

To reduce carbs in homemade kombucha, allow the first fermentation to last longer (e.g., 21-30 days) to give the SCOBY more time to consume the sugar. For flavoring, use non-caloric sweeteners or a smaller amount of fruit.

Yes, adding fruit juice during the secondary fermentation will increase the sugar and carbohydrate content of the final product. The amount of carbs depends on the type and quantity of juice used.

Different kombucha brands have varying carb counts due to differences in fermentation length, the amount and type of sugar used, and the type of flavorings added after fermentation. Some brands prioritize a sweeter taste, leaving more residual sugar.

Traditional kombucha cannot be made without sugar, as it is the fuel for the SCOBY. Brands labeled 'sugar-free' typically use non-caloric sweeteners like stevia or erythritol to achieve sweetness without the sugar. These beverages may not contain the same living probiotics as traditionally fermented kombucha.

Residual sugar is the sugar that remains in the kombucha after the fermentation process is complete. The amount is a direct result of how long and intensely the brew was fermented. The more tart the kombucha tastes, the less residual sugar it contains.