Net Carbs in the UK: Do You Subtract Fibre?
UK labels already exclude fibre. Learn which carbohydrate figure to use, how US labels differ and why polyols need separate care.
Published Updated
No: do not subtract fibre from the carbohydrate figure on a UK food label. Start with the back-of-pack carbohydrate line, then calculate the portion you will eat.
Keep the printable UK label cheat sheet on your phone for shopping.
Why UK and US labels are different
UK nutrition declarations list carbohydrate and fibre separately. Polyols, unlike fibre, fall within the carbohydrate definition. The UK government’s technical nutrition-labelling guidance explains the declaration format.
A US Nutrition Facts panel instead includes dietary fiber within Total Carbohydrate. This is why American keto guides often tell readers to subtract fiber. The FDA’s label guide explains what the US total includes.
Those instructions start from a different label system. Applying them to a UK pack removes fibre twice. “Net carbs” is not an extra subtraction you need to perform on a standard UK label, nor a universal insulin-dosing rule.
How to recognise the label on an imported product
Read the whole nutrition panel, including any UK importer sticker. A US panel commonly says “Nutrition Facts”, “Total Carbohydrate” and “Dietary Fiber”. UK panels commonly give “Carbohydrate” and “Fibre” separately, per 100g or 100ml.
Spelling alone is not enough to establish which rules a label follows. If two panels disagree or the import format is unclear, ask the manufacturer rather than combining figures from different panels.
Worked example: calculate your portion
This is an illustrative label, not a real product recommendation:
| Nutrition | Per 100g |
|---|---|
| Carbohydrate | 8g |
| Of which sugars | 2g |
| Fibre | 12g |
For a 30g portion, calculate 8 × 30 ÷ 100 = 2.4g carbohydrate. Do not subtract the 12g fibre or use the 2g sugars figure instead of carbohydrate. Fibre can be higher than carbohydrate because the figures are separate.
Use the corresponding volume calculation for a label declared per 100ml. Keep prepared and unprepared weights consistent with the label instructions.
Polyols: a separate question
Sugar alcohols such as erythritol, maltitol, sorbitol and xylitol may appear in bars, sweeteners and sugar-free confectionery. They are included in UK carbohydrate, but their absorption and effects are not identical.
Do not treat “sugar-free” or a manufacturer’s front-of-pack “net” claim as proof of zero carbohydrate. Check both the ingredients and the nutrition panel. We keep the declared carbohydrate on our product cards rather than silently adjusting it for polyols.
Diabetes UK explains that polyol counting for insulin adjustment is uncertain and should be discussed with your healthcare team. This page does not recommend a universal full- or half-subtraction rule.
What about diabetes and carb counting?
Use the carbohydrate line, not just “of which sugars”. Follow the method and portion guidance agreed with your diabetes team, especially for imported foods or products containing polyols. See Diabetes UK’s introduction to carb counting.
This is general label-reading information, not personalised medical or insulin-dosing advice. Discuss substantial carbohydrate changes with your healthcare team if you use glucose-lowering medication.
Frequently asked questions
Do I need to subtract fibre from carbs on UK food labels?
No. Use the Carbohydrate figure on a UK nutrition label. Fibre is listed separately and has already been excluded; subtracting it again understates the carbs.
What is the difference between UK and US carb labelling?
UK Carbohydrate excludes fibre. US Total Carbohydrate includes dietary fiber, so US net-carb calculations start from a different number. Do not apply US subtraction advice to a UK label.
Why do some UK products show more fibre than carbohydrate?
They are separate figures. A product can have more fibre than carbohydrate; this does not create negative carbs or justify another subtraction.
Do I need to subtract erythritol or other polyols from carbs on UK labels?
Polyols are included in UK carbohydrate and need separate consideration. Their effects vary; do not automatically subtract all polyols or use a generic formula for insulin dosing. Ask your diabetes team for individual advice.
Put the rule into practice
- UK supermarket guides — verified product cards with individual check dates.
- Compare UK supermarkets — plan your shopping route.
- Low-carb food list — everyday meal ingredients.
- UK label cheat sheet — a printable portion reminder.
Editorial guidance reviewed 18 September 2026. This is not a new verification date for products linked from this page.