Keto Cornstarch & Thickener Substitutes: The Best Low-Carb Swaps

The best low-carb substitute for cornstarch is xanthan gum — roughly 1/4 teaspoon replaces 1 tablespoon of cornstarch and thickens about 1 cup of liquid, for close to 0 g net carbs versus roughly 7 g net carbs from the same amount of cornstarch. Glucomannan, guar gum, psyllium husk, ground flaxseed, and unflavored whey protein isolate each thicken well too, and each fits a slightly different recipe.

Cornstarch is a small ingredient with an outsized carb cost: a single tablespoon used to thicken gravy, stir-fry sauce, or pie filling adds about 7 g net carbs on its own, with none of that offset by fiber.¹ On a 20 to 50 g daily budget, that's real ground given up for a spoonful of powder.² The substitutes below thicken just as effectively — some more effectively — for a fraction of the carbs, so nothing about the texture of your sauce, soup, or gravy has to change. Check the keto food list if you're unsure whether a thickener or its recipe fits your day, and see the keto flour substitute guide if you need a baking-flour swap rather than a thickener.

What's the Best Low-Carb Substitute for Cornstarch?

Xanthan gum is the best all-around low-carb substitute for cornstarch because it thickens at a tiny fraction of the volume, works in both sweet and savory recipes, and carries close to 0 g net carbs per use. It's a fermented plant-fiber powder, sold in the baking aisle of most grocery stores, and it's the ingredient most keto recipe developers already reach for instead of cornstarch or flour.

1. Xanthan Gum: Best Overall

Xanthan gum thickens roughly 10 to 12 times more powerfully than cornstarch by volume, so about 1/4 teaspoon does the work of 1 tablespoon of cornstarch in a cup of liquid, for close to 0 g net carbs. It works in hot or cold liquids, holds up to reheating better than a cornstarch slurry, and has no detectable flavor at normal use levels. The only failure mode is overuse: too much turns a sauce gluey or stringy, so add it in small increments.

2. Glucomannan (Konjac Powder): Best for Glossy Sauces and Pie Fillings

Glucomannan, made from konjac root, is even more powerful than xanthan gum and produces a clearer, glossier finish, which makes it a favorite for fruit pie fillings, Asian-style sauces, and anything meant to look shiny rather than opaque. Use about 1/4 teaspoon per cup of liquid for close to 0 g net carbs, whisking it in slowly since a few seconds of over-mixing can make it clump.

3. Guar Gum: Best for Cold Thickening

Guar gum thickens without any heat at all, which makes it the pick for cold applications cornstarch can't touch: salad dressings, cold soups, smoothies, and no-cook sauces. Use about 1/4 teaspoon per cup of liquid, for close to 0 g net carbs. It's more prone to a slick or "slimy" texture than xanthan gum if you add too much, so start light.

4. Psyllium Husk Powder: Best for Gravies with Real Body

Psyllium husk is almost pure soluble fiber, so it thickens by absorbing and gelling liquid rather than by pure starch chemistry, giving gravies a heartier, less gluey mouthfeel than the gums above. Use about 1 to 2 teaspoons per cup of liquid, which works out to roughly 1 g net carbs per teaspoon. It can turn a light-colored sauce slightly gray, so it's best in gravies and stews that are already opaque.

5. Ground Flaxseed: Best for Stews and Chili

Ground flaxseed (flax meal) thickens more gradually than the gums, simmering into a stew or chili over 5 to 10 minutes rather than gelling instantly. Use about 1 tablespoon per cup of liquid, for roughly 2 g net carbs. It has a mild nutty flavor and a faint tan color, so it disappears easily into chili, meaty stews, or gravies but stands out in a clear or pale sauce.

6. Unflavored Whey Protein Isolate: Best for Cream Sauces

Unflavored whey protein isolate thickens cream-based sauces and gravies while adding protein instead of empty starch. Whisk about 1 tablespoon into hot — not boiling — liquid off direct heat for roughly 1 g net carbs; too much heat or a hard boil can cause it to clump or curdle instead of thickening smoothly. It's the least versatile pick on this list since it only really shines in dairy-based sauces.

How Do These Cornstarch Substitutes Compare?

Substitute	Net carbs	Swap ratio (vs. 1 tbsp cornstarch)	Best for
Xanthan gum	~0 g per 1/4 tsp	1/4 tsp = 1 tbsp cornstarch	All-purpose sauces & gravies
Glucomannan (konjac)	~0 g per 1/4 tsp	1/4 tsp = 1 tbsp cornstarch	Glossy sauces & pie fillings
Guar gum	~0 g per 1/4 tsp	1/4 tsp = 1 tbsp cornstarch	Cold dressings & smoothies
Psyllium husk powder	~1 g per tsp	1–2 tsp = 1 tbsp cornstarch	Gravies with real body
Ground flaxseed	~2 g per tbsp	1 tbsp = 1 tbsp cornstarch	Stews & chili
Whey protein isolate	~1 g per tbsp	1 tbsp = 1 tbsp cornstarch	Cream sauces
Cornstarch (baseline)	~7 g per tbsp	—	Not keto-friendly

Run any recipe through the net-carb calculator once you swap the thickener, since the rest of the dish's carbs don't change — only the thickener does.

How Do You Thicken a Sauce with Xanthan Gum?

Pull the pan off high heat, sprinkle 1/4 teaspoon of xanthan gum evenly over 1 cup of liquid while whisking constantly, let it hydrate for 30 seconds, then check the thickness before adding more. Going slowly matters more than the exact amount — xanthan gum keeps thickening for a few seconds after it hits the liquid, and it's far easier to add a pinch more than to fix an over-thickened, gluey sauce.

1. Pull the pan off high heat. A low simmer or no heat at all is fine — xanthan gum doesn't need to boil to activate, unlike cornstarch.
2. Sprinkle it in evenly. Add it a little at a time over the surface, whisking hard, rather than dumping it in one spot where it will clump.
3. Wait 30 seconds. Let it fully hydrate before judging the texture; it keeps thickening slightly after mixing.
4. Add more only in small pinches. An extra 1/8 teaspoon at a time is usually plenty if the sauce is still thin.
5. Serve it fresh. A hard boil or multiple reheats can thin a xanthan-thickened sauce back out, so add it close to serving time.

The same basic method — off high heat, added slowly, checked before adding more — works for glucomannan and guar gum too. To dial in your macros around any of these swaps, see how to calculate your keto macros, and start from the low-carb substitutes hub for swaps to every other high-carb staple.

Frequently Asked Questions

Is cornstarch keto-friendly?

Not in normal amounts. One tablespoon of cornstarch has about 7 g net carbs and no fiber to offset it, which is a meaningful bite out of a 20 to 50 g daily budget for something used only to thicken a sauce.

What's the best keto substitute for cornstarch in gravy?

Xanthan gum is the most reliable choice for gravy. About 1/4 teaspoon per cup of liquid matches cornstarch's thickening power for close to 0 g net carbs, with a texture most people can't tell apart from a traditional gravy.

Can I use almond flour or coconut flour to thicken a sauce?

You can, but they add more carbs (roughly 1 to 3 g net carbs per tablespoon) and a slightly grainy texture, so a gum or glucomannan is usually a cleaner swap for a smooth sauce. See the keto flour substitute guide for baking-specific ratios.

Does xanthan gum change the taste of a recipe?

No, xanthan gum is flavorless at the small amounts needed to thicken a sauce. Using well over 1/2 teaspoon per cup can start to taste faintly bitter or leave a slick mouthfeel, which is another reason to add it gradually.

Can these substitutes thicken cold recipes, like dressings?

Yes. Guar gum and glucomannan both thicken without any heat, which makes them better than cornstarch for cold salad dressings, cold soups, and smoothies, since cornstarch needs to be cooked to activate.

Works cited

1. FoodData Central — U.S. Department of Agriculture — August 19, 2026 https://fdc.nal.usda.gov/
2. Diet Review: Ketogenic Diet for Weight Loss — Harvard T.H. Chan School of Public Health, Nutrition Source — August 19, 2026 https://nutritionsource.hsph.harvard.edu/healthy-weight/diet-reviews/ketogenic-diet/

Article history

1. August 23, 2026Updated
2. August 19, 2026First published