A box says "keto" in big letters and "only 2g net carbs" on the front. Then you flip it over and find maltitol, tapioca syrup, and a serving size of half a bar. This is the single most common way people accidentally knock themselves out of ketosis while paying a premium for the privilege. The front of the package is marketing. The back is the truth, and it takes about 15 seconds to read once you know what you're looking at.
We read these labels for a living, and the pattern is depressingly consistent: added sugars hiding under unfamiliar names, sugar alcohols that still raise blood glucose, and "net carb" math that only works if you eat a tiny portion. Here is exactly how to spot the tricks so you stop wasting money on products that aren't actually low-carb.
Ignore the front entirely and start with the Nutrition Facts panel. Check the serving size first, because a bar or bag often lists numbers for half the package. If the total carbs are 25g and the label brags about "3g net carbs," that gap is made up of fiber and sugar alcohols, and you need to know which. Net carbs are total carbs minus fiber and minus sugar alcohols, but that subtraction is only honest when the sugar alcohol is a genuinely inert one like erythritol.
Then read the full ingredient list, not just the highlights. Ingredients are listed by weight, so if a sweetener or syrup shows up in the first three items, it makes up a big chunk of the food. A truly low-carb product usually leads with things like almond flour, nuts, cheese, or coconut, with sweeteners further down. If sugar in any form is near the top, put it back.
Sugar alcohols are the biggest source of "net carb" confusion. Erythritol is the friendliest one: it has close to zero effect on blood sugar and gets almost fully excreted, so subtracting it from total carbs is fair. Allulose (technically a rare sugar, not an alcohol) and monk fruit behave similarly and are worth it. These are the sweeteners you want to see.
Maltitol is the one to watch. It's cheap, which is why so many budget "keto" bars use it, and it raises blood glucose noticeably (its glycemic index sits around 35, far from zero). A bar with 15g of maltitol can behave more like 8 to 10g of real carbs in your body, even though the label proudly subtracts all of it as "sugar alcohol." It also causes serious digestive distress for a lot of people. Sorbitol and isomalt land in a similar gray zone.
Our honest verdict: treat erythritol, allulose, and monk fruit as safe to subtract, but count roughly half of any maltitol or sorbitol as real carbs when you're deciding whether a product fits your day. If the entire "net carb" claim depends on subtracting maltitol, the real number is higher than advertised.
Sugar wears a lot of costumes. Watch for these names near the top of any list: tapioca syrup, tapioca starch, cane sugar, brown rice syrup, coconut sugar, honey, agave, maltodextrin, dextrose, and "evaporated cane juice." Maltodextrin deserves a special callout, it's often used as a bulking agent and has a glycemic index higher than table sugar, yet it can slip in under "fiber" or filler names.
Fiber claims can be inflated too. Some products dump in isomalto-oligosaccharides (IMO fiber) and then subtract all of it as fiber, but research shows a good portion of IMO digests like sugar and raises blood glucose. If a bar claims 12g of fiber and it's all IMO, be skeptical. Real fiber from almonds, flax, chia, and coconut is trustworthy; a mystery "fiber" that makes a candy-like product magically low in net carbs usually isn't.
The tell that ties it all together: a long ingredient list, a tiny serving size, and net carb math that only works because of maltitol or IMO fiber. When you see all three, you're looking at a snack dressed up as keto. The good news is that plenty of genuinely low-carb products exist at a fair price, and once you can read the label you'll spot them fast.