When counting carbs, do I subtract sugar alcohol?

November 22, 2025 •

4 min read

According to the American Diabetes Association, the term "net carbs" has no legal definition, which can make things confusing. The short answer to whether to subtract sugar alcohol is: yes, but not always entirely, and it depends on the type.

Quick Summary

This guide explains the process of calculating net carbs by subtracting fiber and sugar alcohols from total carbohydrates. Learn which sugar alcohols have the least impact on blood sugar and how different types affect your daily count.

Key Points

Know the difference: Understand that net carbs, not total carbs, are the focus for low-carb and keto diets.
Subtract with caution: Not all sugar alcohols can be fully subtracted from total carbs; the type matters.
Erythritol is an exception: You can subtract 100% of erythritol due to its minimal impact on blood sugar.
Use the 'half-and-half' rule: For most sugar alcohols like maltitol and sorbitol, subtract only half of the grams listed.
Beware of high-GI sugar alcohols: Maltitol syrup, in particular, has a higher glycemic impact and should be limited.
Monitor your individual response: Because everyone reacts differently, pay attention to how your body responds to specific sugar alcohols.
Read the ingredient list: Look for specific sugar alcohol names, as manufacturers aren't always required to list them on the main label.

Understanding Total vs. Net Carbs

When following a low-carb or ketogenic diet, the terms 'total carbs' and 'net carbs' are used frequently. It's crucial to understand the distinction to manage your intake accurately. Total carbohydrates, as listed on a nutrition label, include all types of carbohydrates present in a food item. Net carbs, on the other hand, represent the carbohydrates that your body can actually digest and convert into glucose, thereby affecting your blood sugar.

The calculation for net carbs is generally simple: subtract dietary fiber and sugar alcohols from the total carbohydrates. The logic is that the body does not fully digest these components, meaning they have a lesser impact on blood sugar levels. However, as we will explore, this simple subtraction is not always accurate, particularly when it comes to sugar alcohols.

The Role of Dietary Fiber

Dietary fiber is a type of carbohydrate that your body cannot fully break down. It passes through the digestive system largely intact, and in doing so, it can help regulate blood sugar levels and improve digestive health. Because it is indigestible, dietary fiber is typically subtracted entirely from the total carbohydrate count to determine net carbs.

The Nuance with Sugar Alcohols

Sugar alcohols, also known as polyols, are carbohydrates that taste sweet but are only partially absorbed by the body. This means they contribute fewer calories and have a lesser effect on blood sugar than regular sugar. While many low-carb and keto products market themselves based on low net carbs derived from sugar alcohols, the impact can vary significantly depending on the specific type of sugar alcohol used. This variation is why a blanket subtraction of all sugar alcohol grams is not always advisable.

A Guide to Subtracting Sugar Alcohols

To accurately count net carbs, it's essential to know how different sugar alcohols are metabolized. The best practice is to know what you are consuming rather than assuming all sugar alcohols are created equal. Below is a breakdown of how to handle specific types.

Full Subtraction: Erythritol

Erythritol is a sugar alcohol with a glycemic index of near zero. It is almost entirely absorbed in the small intestine and excreted in urine, which means it has virtually no effect on blood sugar. For products sweetened with erythritol, you can subtract the full amount listed under 'Sugar Alcohol' from the total carbs.

Partial Subtraction: The "Half-and-Half" Rule

For many other common sugar alcohols, such as maltitol, sorbitol, and xylitol, the rule is to subtract only half of the grams listed. These sugar alcohols are only partially digested, so they do have some impact on blood sugar and still provide calories. For individuals with diabetes or on a strict low-carb diet, monitoring blood sugar after consuming products with these sweeteners is especially important.

No Subtraction: Watch for Unlisted Types

Some less common sugar alcohols or sweeteners, particularly those with a higher glycemic index, should not be subtracted at all. Additionally, food manufacturers are not required to list sugar alcohols on the nutrition label unless they make a specific health claim about sugar alcohols or sugars. Always check the ingredient list for names like 'maltitol syrup,' which has a higher glycemic impact than plain maltitol.

Comparison Table: Common Sugar Alcohols


Sugar Alcohol	Glycemic Index (GI)	Recommended Subtraction	Considerations
Erythritol	~0	Full (100%)	Best choice for keto; may cause mild digestive issues in large doses.
Xylitol	~7-13	Half (50%)	Moderately low GI; can cause more GI distress than erythritol; toxic to dogs.
Sorbitol	~9	Half (50%)	Lower GI; often used in sugar-free candy; known laxative effect in larger amounts.
Maltitol	~35-52	Half (50%)	Higher GI than most other SAs; closer caloric value to sugar; subtract only half or potentially zero if sensitive.
Isomalt	~9	Half (50%)	Low GI; used in candies and pastries; moderate consumption recommended.
Lactitol	~3-6	Half (50%)	Low GI; derived from milk; may be tolerated well in moderation.

The Importance of Moderation and Individual Response

While subtracting sugar alcohols can be a helpful tool for tracking net carbs, it is not a perfect science. The body's response to these sweeteners is highly individual, and consuming large quantities of any sugar alcohol can lead to gastrointestinal issues like bloating, gas, and diarrhea. Furthermore, some individuals may experience a blood sugar spike from sugar alcohols that others do not.

Conclusion: A Balanced Approach to Carb Counting

Ultimately, understanding how to count net carbs by subtracting sugar alcohols requires a nuanced approach. It’s not a simple, universal rule, but a matter of understanding which types you can confidently subtract and which require more caution. For those on a ketogenic or low-carb diet, paying attention to the specific sugar alcohols in processed foods is key to staying within your daily carb limits and avoiding unwanted blood sugar spikes. For a comprehensive list of sugar alcohols and their properties, the International Food Information Council (IFIC) website is a valuable resource.

Lists of Sugar Alcohols and Side Effects

Sugar Alcohols to Check for in Ingredients:

Erythritol
Xylitol
Sorbitol
Maltitol
Isomalt
Lactitol
Mannitol
Hydrogenated Starch Hydrolysates

Potential Side Effects of Excessive Consumption:

Bloating
Gas
Abdominal cramps
Diarrhea (laxative effect)
Possible disruption of gut bacteria

How to Calculate Net Carbs Step-by-Step

Find the nutrition label: Locate the 'Total Carbohydrate', 'Dietary Fiber', and 'Sugar Alcohol' lines.
Subtract fiber: Subtract the full amount of dietary fiber from the total carbs.
Check the sugar alcohol type: Refer to the comparison table or ingredient list to see which sugar alcohols are used.
Subtract sugar alcohol: Subtract either half (for most) or the full amount (for erythritol only) of sugar alcohols.
Final calculation: Total Carbs - Fiber - (Adjusted Sugar Alcohol) = Net Carbs.

Outbound Link

For further information on food science and sweeteners, visit the International Food Information Council (IFIC) website.

Frequently Asked Questions

No, you cannot subtract all sugar alcohol grams. While erythritol can be fully subtracted, most others like maltitol and sorbitol should only be partially (usually 50%) deducted because they still impact blood sugar to some extent.

Erythritol is widely considered the best sugar alcohol for a keto diet. It has a near-zero glycemic index and is not metabolized by the body, so it does not spike blood sugar or insulin.

Sugar alcohols can cause digestive issues like bloating, gas, and diarrhea because they are not fully absorbed by the body. They travel to the large intestine where gut bacteria ferment them, which can cause discomfort, especially in large quantities.

No, the term 'net carbs' has no official legal definition and is not recognized by regulatory bodies like the FDA or the American Diabetes Association. It is a concept used primarily by low-carb and keto communities.

To calculate, first, subtract the full amount of dietary fiber. Then, subtract the appropriate portion of sugar alcohols (e.g., 50% for most, 100% for erythritol). Add these subtractions together and deduct from the total carbohydrate count.

If the label doesn't specify the type of sugar alcohol, it's safest to assume it's one that requires a partial deduction or to count half of the total sugar alcohol amount to be conservative with your carb count.

No, their effect on blood sugar varies significantly. Some, like erythritol, have almost no effect, while others, such as maltitol, have a higher glycemic index and can cause a more noticeable blood sugar increase.