Guide

The Nutrition Facts label is one of the most useful tools for blood sugar management — if you know how to read it. Most people glance at calories and maybe total fat, then move on. For anyone managing diabetes or monitoring glycemic load, the carbohydrate section is where the actionable information lives. Let me walk through it line by line.

Total carbohydrates: the top-line number

Total carbohydrates on a nutrition label include all carbohydrate types: sugars, fiber, starch, and sugar alcohols. This is the number the FDA requires. It represents everything in the food that your body might process as carbohydrate, regardless of how quickly or slowly it affects blood sugar.

For a rough GL estimate, total carbs is the starting point. But it's a blunt tool — fiber and sugar are counted the same, even though fiber has essentially no glycemic impact.

Dietary fiber: subtract this for a better estimate

Dietary fiber is listed as a subcategory under total carbohydrates. Fiber is a carbohydrate your body cannot fully digest. Soluble fiber slows glucose absorption — beneficial for blood sugar. Insoluble fiber passes through mostly intact. Neither type produces a significant blood glucose response.

The formula for "available carbohydrates" — the carbs that actually affect blood sugar — is: total carbohydrates minus dietary fiber. A food with 30 grams of total carbs and 8 grams of fiber has 22 grams of available carbohydrates. That's the number that matters for GL calculations.

"Net carbs": not what you think

The term "net carbs" appears on many food packages, particularly those marketed to low-carb and keto consumers. Here's what matters: "net carbs" is not an FDA-regulated term. There is no official definition. Different brands calculate it differently.

The most common formula is total carbs minus fiber minus sugar alcohols. But this is misleading for blood sugar purposes because not all sugar alcohols are equal — some affect blood sugar significantly, and some barely do. By subtracting all of them, the "net carbs" number can make a product look much more diabetes-friendly than it actually is.

In my read of the evidence, the numbers to rely on are total carbohydrates and fiber — the figures the FDA requires — rather than "net carbs" claims, which are essentially marketing.

Sugars, added sugars, and what they tell you

Under total carbohydrates, you'll see "Total Sugars" and, indented beneath it, "Includes X grams Added Sugars." Here is what each means:

• Total Sugars — includes both naturally occurring sugars (lactose in milk, fructose in fruit) and added sugars. This number alone doesn't tell you much about glycemic impact because natural sugars in whole foods behave differently than added sugars.
• Added Sugars — sugars added during manufacturing. This is the more useful number. High added sugar generally correlates with higher glycemic impact because these sugars are rapidly absorbed without the fiber, fat, and protein matrix that slows down natural sugars in whole foods.

A useful rule of thumb: if added sugars exceed 25% of total carbohydrates, the product is likely high-GL regardless of what else is in it.

Sugar alcohols: the messy middle ground

Sugar alcohols (erythritol, maltitol, sorbitol, xylitol) are used as sweeteners in many "sugar-free" and "low-carb" products. They're listed on the label, but their blood sugar impact varies enormously by type:

• Erythritol — GI of 0. Does not affect blood sugar at all. This is the gold standard of sugar alcohols for diabetes management.
• Xylitol — GI of about 7. Minimal blood sugar impact.
• Sorbitol — GI of about 9. Low impact.
• Maltitol — GI of about 35. This one is the problem. Maltitol has a meaningful glycemic impact, and it is the most commonly used sugar alcohol in "sugar-free" candy, chocolate, and baked goods. "Sugar-free" products made with maltitol can raise blood sugar significantly.
• Isomalt — GI of about 9. Low impact but can cause digestive discomfort in larger amounts.

The bottom line: check which sugar alcohol is used. Erythritol and xylitol are genuinely low-impact. Maltitol is not. "Sugar-free" does not mean "blood-sugar-free."

"Sugar-free" and "no sugar added": what they don't mean

"Sugar-free" means the product contains less than 0.5 grams of sugar per serving. It does not mean carb-free. A sugar-free cookie can still contain 15 grams of carbohydrates from flour and other ingredients — and those carbohydrates will affect blood sugar.

"No sugar added" means no sugar was added during processing. But the product may still contain significant natural sugars. "No sugar added" fruit juice concentrate, for example, is still essentially fruit sugar and has a high GL.

Neither claim tells you what you actually need to know: how many available carbohydrates are in a serving, and what is the GI of this food?

The "whole grain" and "multigrain" problem

A product labeled "whole grain" must contain whole grain ingredients, but there is no requirement for how much. A bread that is 51% refined flour and 49% whole grain can be labeled "made with whole grains." The glycemic impact of such a bread is not meaningfully different from white bread.

"Multigrain" is even less meaningful — it just means more than one type of grain was used. All of those grains could be refined.

For bread and grain products, fiber content is the most useful label figure. If a slice of bread has 4 or more grams of fiber, it likely contains a meaningful amount of intact whole grain. If it has 1 to 2 grams, it's probably mostly refined flour regardless of what the front of the package says.

Serving size: the number that changes everything

All nutrition label values are per serving — and serving sizes are often smaller than what people actually eat. A serving of cereal is typically 3/4 cup to 1 cup; most people pour 1.5 to 2 cups. A serving of crackers might be 6 crackers; most people eat 10 to 15. A serving of ice cream is 2/3 cup; most people eat 1 to 1.5 cups.

Before using any label value for GL estimation, check the serving size and honestly compare it to how much you actually eat. If you eat twice the listed serving, double all the numbers — including carbohydrates.

Estimating GL from a label

To estimate the GL of a packaged food from its label, you need two things: the available carbohydrates per serving (total carbs minus fiber) and the food's GI value (not listed on labels, but available from databases like the Sydney University GI Database).

The formula: GL = (GI x available carbs in grams) / 100.

For example, a serving of oatmeal with 27 grams of total carbs and 4 grams of fiber has 23 grams of available carbs. Oatmeal has a GI of about 55. GL = (55 x 23) / 100 = 12.65, which rounds to a medium GL of about 13.

This manual calculation is useful for packaged foods but tedious for complete meals with multiple ingredients. That is where Glyc automates the process — it performs this calculation for every ingredient in a recipe, adjusting for actual serving sizes and preparation methods, and gives you a total per-serving GL for the complete meal.

A practical label-reading checklist

1. Check the serving size. Is it realistic for how much you actually eat?
2. Look at total carbohydrates and subtract fiber to get available carbs.
3. Check added sugars. If high relative to total carbs, the product is likely high-GL.
4. If sugar alcohols are listed, check which type. Maltitol counts. Erythritol doesn't.
5. Ignore "net carbs" claims on the front of the package.
6. Ignore "sugar-free" and "whole grain" claims without checking the actual numbers.
7. Look at protein and fat content — higher amounts of both slow glucose absorption.

Reading food labels takes about 15 seconds once you know what to look for. Those 15 seconds give you more useful information about a food's blood sugar impact than any marketing claim on the front of the package.