The number that decides this is glycemic impact, not grams
A sweetener can carry carbohydrate and still leave you in ketosis, or carry almost none on paper and raise your blood sugar anyway. What separates them is how much of it your small intestine absorbs. Every sweetener below is ranked on glycemic index — the measured effect on blood glucose, where table sugar is 65.
Anything at or near zero passes through largely unabsorbed and is safe in the quantities a normal person uses. The trouble starts in the middle of the range, where the marketing is loudest.
THE SHORT ANSWER
Allulose and monk fruit for anything. Maltitol never, whatever the front of the packet says.
GI measured against glucose = 100. Table sugar = 65.
Best Choices
GLYCEMIC INDEX 0–1 — NO MEANINGFUL BLOOD SUGAR RESPONSEUse these freely. None of them registers on a glucose meter at ordinary kitchen quantities.
ALL SIX MEASURE 0–1 ON A SCALE WHERE TABLE SUGAR IS 65
RULE OF THUMB
If the ingredients list has one name on it, you are usually fine. Blends are where the filler hides.
THE NET CARB TRICK
The label says 2g. The bar is closer to 13
"Net carbs" is a marketing term, not a regulated one. A manufacturer is free to subtract every gram of fibre and every gram of sugar alcohol from the total carbohydrate and print whatever is left in large type on the front of the box.
That subtraction is honest for erythritol, which is almost entirely excreted. It is not honest for maltitol, which is roughly half absorbed and carries a glycemic index around 35 — half the impact of table sugar, printed as zero.
The fix is mechanical: turn the box over, find which sugar alcohol it actually uses, and only subtract the ones that earn it.
THE ONE RULE
Subtract erythritol and allulose in full. Subtract half of xylitol, sorbitol and isomalt. Subtract none of maltitol — count it as sugar and move on to a different product.
WORKED EXAMPLE
A typical "keto" chocolate bar, sweetened with maltitol
ROUGHLY HALF OF MALTITOL IS ABSORBED — 21G BECOMES ABOUT 11G OF USABLE CARBOHYDRATE, PLUS THE 2G ALREADY DECLARED.
Moderate
GLYCEMIC INDEX 4–13 — SMALL AMOUNTS ONLYThese will not break ketosis in a teaspoon. They will give a fair number of people cramping and worse in a tablespoon, and one of them is lethal to dogs.
SAFETY WARNING — DOGS
Xylitol is fatally toxic to dogs, in quantities as small as a piece of gum.
It triggers a collapse in blood sugar within twenty minutes and can cause liver failure. If you bake with xylitol and own a dog, keep it in a sealed container out of reach, and call a vet immediately on any suspected ingestion — do not wait for symptoms.
WHY BLENDS SIT HERE
Most supermarket "sugar-free" baking blends are not one sweetener but three or four, and the cheap bulking agent is doing most of the work by weight. A blend is only as good as its largest ingredient — read the list in order, and treat anything ending in -itol other than erythritol as a reason to use less than the recipe says.
Baking and cooking with them
01 / CONVERSIONS
Sweetness is not the same as volume
Sugar does structural work in baking — bulk, moisture, browning — and a few grains of stevia cannot replace a cup of it. Granulated blends exist precisely so you can swap by volume without rewriting the recipe.
02 / THE COOLING PROBLEM
Erythritol goes cold and recrystallises
That mint-like chill is erythritol dissolving, and it grits up again as baked goods cool. Allulose does neither — it stays soft, browns like sugar and is the better choice for caramel, ice cream and anything chewy.
03 / FIXING THE AFTERTASTE
Two sweeteners taste better than one
Every high-intensity sweetener has an off-note, and they sit in different places on the tongue. Blending covers the gaps — which is why almost every good commercial product is a blend rather than a single ingredient.
04 / THE STANDING RULE
Read the ingredients, not the front of the pack
Thirty seconds on the back of the box settles every question this page raises. If the first ingredient is erythritol, allulose, monk fruit or stevia, buy it. If it is maltitol, maltodextrin or dextrose, put it back — whatever the front says.
Common questions
Do sweeteners kick you out of ketosis?+
The ones in the best-choices tier do not. Stevia, monk fruit, erythritol and allulose are either unabsorbed or excreted unchanged, and controlled studies show no meaningful glucose or insulin response at normal intakes. Maltitol will, in the quantities found in a whole "sugar-free" chocolate bar. The more common failure is indirect: sweet food keeps the taste for sweet food alive, and for some people a daily dessert reliably leads to the thing that actually ends the diet. That is a behaviour question, not a biochemistry one, and only you can answer it.
What is the best sweetener for baking?+
Allulose for anything that should stay soft, chewy or browned — cookies, caramel, ice cream — because it behaves like sugar in the pan and does not recrystallise. A granulated monk fruit and erythritol blend for cakes, muffins and anything you want to measure cup for cup. Keep pure stevia and pure monk fruit for drinks and sauces where you need sweetness without bulk; they cannot carry a bake on their own, and a recipe that calls for a cup of sugar needs a cup of something.
Why does stevia sometimes taste bitter?+
Stevia leaf contains several sweet compounds, and they do not taste alike. Rebaudioside A and M are clean; stevioside carries the liquorice-metallic bitterness most people object to, and cheaper extracts contain more of it. Genetics play a part too — a sizeable minority taste that bitterness far more strongly than everyone else. Two fixes: buy an extract that names Reb A or Reb M on the label, and use a blend, because erythritol or monk fruit masks the off-note almost completely. Overdosing also makes it worse, so measure rather than pour.
Are "sugar-free" products always keto-safe?+
No, and this is the single most expensive assumption a beginner makes. "Sugar-free" is a legal claim about sucrose, not about carbohydrate. A biscuit sweetened with maltitol and bulked with maltodextrin is sugar-free and will still raise your blood glucose, because maltodextrin has a higher glycemic index than sugar does. Sugar-free syrups, sweets, protein bars and drink powders are all built this way. The label on the front tells you what was left out; only the ingredients list tells you what went in instead.
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