Use in Moderation
Onion
8.30g net carbs per 1 medium onion
Measure carefully, because a whole medium onion runs 8.3 g net carbs, enough to crowd out a tight daily budget. Use a few thin slices or a tablespoon of diced onion for flavor instead of building a dish around it.
Built by Barron Hansen · Last updated July 2026
Nutrition Facts
Fits My Daily Budget?
Set your daily net carb limit to see how one serving fits.
One serving uses 42% of your 20g daily budget.
Plan the rest of your day
Good to Know
Onions get sweeter and more carb-dense as they caramelize, since slow cooking concentrates their natural sugars, so a pile of caramelized onions adds up fast. Green onions and chives give you that allium kick for far fewer carbs, with a tablespoon of chopped scallion tops sitting well under 1 g net. Watch packaged French onion dips and crispy fried onion toppings (like French's), which often pack added sugar and wheat flour breading on top of the onion itself.
Is Onion Keto? The Full Answer
Onion contains 8.30g net carbs per 1 medium onion (10.20g total carbs minus 1.90g fiber). Measure carefully, because a whole medium onion runs 8.3 g net carbs, enough to crowd out a tight daily budget. Use a few thin slices or a tablespoon of diced onion for flavor instead of building a dish around it.
On a standard ketogenic diet, most people target 20-25g net carbs per day. A single serving uses 42% of a 20g daily carb limit. Track your portions carefully and account for other carbs in your meals.
Better Keto Swaps
Onions are tasty, but they add up fast. One medium one carries 8.3 g net carbs, which can eat a big chunk of your daily budget. Here are some lower-carb stand-ins. First, green onions (scallions): use just the green tops and you get a similar bite for about 1.1 g net carbs per 15 g handful. Second, chives, which bring that mild allium flavor at roughly 0.1 g net carbs per tablespoon, perfect as a finishing sprinkle. Third, leeks in small amounts, around 2 g net carbs for a 25 g slice, good when you want softer, sweeter notes without going full onion. A pinch of onion powder (about 1.7 g net carbs per teaspoon) also works when you just want the taste, not the volume.
Track Your Ketone Levels
The Keto-Mojo meter is the gold standard for confirming you're actually in ketosis. Know your numbers - don't guess.