Are Onions Keto? Carbs & Calories in Onion


A half cup of chopped raw onions contains 6 grams of carbs and 1 gram of fiber.  If eaten in moderate amounts, onions can absolutely fit into a low-carb diet plan.

Although they are fairly high in carbs by weight, onions are typically consumed in small amounts because of their pungent, full-bodied flavor.

is onion keto

Are Onions Keto Friendly? 

Since Keto dieters can consume 30 grams of net carbohydrates per day and still remain in ketosis, a little onion can fit well within these limits. However, the serving size of onions should be kept in moderation, depending on the type of onion being consumed.

Melt Fat Fast with Keto Diet -> Pick Your Plan!

The lowest carb type of onions to consume on Keto are Green onions (also known as scallions) as they contain only 4.4 grams of net carbs per 100 grams.

Health Benefits of Onions

  • Onions are high in the antioxidant called quercetin, which helps lower blood pressure.
  • Onions are low in calories, high in calcium, and high in vitamin C.
  • Onions are 97% water to help keep you hydrated.
  • Onions have been used for many years to help rid symptoms of the common cold by placing a layer of sliced onions on your chest and wrapping the sick person in warm blankets.
  • Packed with nutrients, onions are nutrient-dense. They’re high in vitamins and minerals.
  • Onions support heart health and digestive health.
  • Onions are loaded with antioxidants and contain anti-cancer compounds.
  • Onions control blood sugar and boost bone density.
  • Onions have antibacterial properties.

Carbs, Calories and Fiber in Onions

There are 27 different types of onions in existence.  The most common types that people eat include: red onions, yellow onions, spring onions, sweet onions, green onions, and shallots. Most of these types contain different amounts of vitamins and minerals, but they generally contain between 7 and 8 grams of carbohydrates in every 100 grams.

Shallots are an exception to this rule.  Shallots are not considered to be low-carb vegetables. With 17 grams of carbs per 100 gram serving, with only 3.2 grams coming from fiber, total net carbs for this type of onion clocks in at around 14 grams. 

Yellow onions are also exponentially higher in calories than the other types, so they should be watched if you’re following a calorie reduction plan.  With that being said, most people don’t overeat onions, due to their robustly strong flavor.

Let’s take a closer look at a few of the most common types of onions we use for cooking and eating.  View the following chart for the nutritional breakdown of various types of onions on the market.

Based on a 100 gram serving:
Onion Type Calories Carbs Fiber
Shallots 72 16.8 grams 3.2 grams
Spring Onions 32 7.3 grams 2.6 grams
Sweet Onions (Vadalia) 32 7.6 grams 0.9 grams
Green Onions (Scallions) 32 7 grams 2.6 grams
Yellow Onions 132 7.9 grams 1.7 grams
Red Onions 37 7.9 grams 1.5 grams
is onion keto friendly

Origin of Onions

The onion, also named the bulb onion or the common onion, is a vegetable that is the most widely cultivated species of the genus Allium. Close relatives of the onion family include garlic, shallots, leeks, and chives.

Interesting Onion Facts

  • Onions are a very easy vegetable to grow. They grow in just about any type of soil as long as they get sun and water.
  • Onions really do make you cry. That’s because of the sulfuric acid in them. The acid isn’t dangerous to consume, but it sure does make your eyes burn.
  • To peel or cut an onion without crying, cut the root end last. If the onion is cold, you can cut it while holding the onion under cold running water to stop the tears.
  • Ancient Egyptians worshiped the onion bulb, believing its concentric rings and sphere shape to be symbols of eternal life.  Onion traces have even been discovered in the eye sockets of mummified remains found in ancient burial tombs.
  • There is an old wives tale that claims the thicker the onion’s skin, the colder the winter will be that year.
  • The record of the largest onion in the world weighed in at over 10 pounds!
  • Chewing parsley cures “onion-breath”.

Which Types of Onions are Best for Keto? 

Spring onions are considered suitable for a low-carb diet, as they have 7.3 grams of carbohydrates, 2.6 grams of which come from fiber.  By subtracting the fiber amount from the carbohydrate amount, net carbs are brought down to only 4.7 grams in every 100 gram serving.

Green onions/scallions are another great option for Keto as they contain only 7 grams of carbs and 2.6 grams of fiber, which tallies up to only 4.4 grams of net carbs per serving.

are onions low carb

Other Types of Onions

Most onions are purple, yellow, green or white in color. All onions taste like onions; however, some are sweeter and others are more pungent. Different types may also be grown differently.

Pearl onions are tiny white onions with a sweet flavor. They are typically used to make pickled onions.

Bermuda onions are large onions with a thicker skin, but milder flavor.

Egyptian onions have a very robust flavor. Both the bulb and the tops can be consumed.

Super-sweets are also used in the same way Vidalia onions are used. Just like their name, these onions are really and truly super-sweet. People eat them raw on sandwiches, in salads and in salsas.

Chives are a perfect seasoning for numerous dishes. They provide a sharp kick to any recipe and are a great way to spice up salads and soups.

Red wing onions are a mild type of onion that tastes great raw, making them the perfect choice for sandwiches or  salads.

Leeks are another type of onion that are one of the most versatile types.  They make great soups and are delicious slow cooked with meats in a stew. Leeks also pair perfectly with bacon, a combination we can all get behind!

Welsh onions are perfect for making stir fry.  They closely resemble green onions, though they’re usually bigger.  They’re mainly used in Asian cooking, like stir-fried vegetable dishes.

Spanish onions are often confused with yellow onions, as they are similar in appearance; however, the Spanish onion is sweeter and has a lower water content.

Ways to Enjoy Onions In Keto

onion low carb

Onions are a delicious, nutritious food that can be consumed in a variety of ways. Add a serving of onions to season your favorite Keto recipes.  Green onions are especially low in carbs and versatile.  They can be used to garnish soups, spice up salads or sandwiches, and to season dips.

Because people do not generally eat too many onions at once, due to their strong flavor, it is difficult to overeat onions.  However, be mindful when consuming caramelized or sautéed onions, as these are easier to eat in larger amounts.

Cooking Methods

Whether fried, broiled, sweated, sautéed, roasted, or pickled, there are many ways to enjoy onions on Keto.  Just make sure you don’t overdo it and eat too many. 

With that being said, if are a person who loves caramelized onions, make sure you use a food scale to measure out a 100 gram serving.  Carmelized and fried onions are so tasty, many Keto dieters complain about overindulging on them, not realizing they are consuming so many carbs. 

Onion rings (dipped in flour batter and deep fried) should also be avoided on low carb diets as they’re high in calories, fat and carbs. Eating onion rings regularly will likely counteract your diet success.  Eating too many onions in this way could exceed your daily carb quota, pushing your body out of ketosis.

Keto Tip: The trick to preparing your favorite fried foods, like onion rings on Keto, is to make recipe substitions. You can make your own homemade onion rings using low carb coconut flower or almond flower in the batter, instead of high carb white flour.

Melissa Marshall

A litigation paralegal and writer. Her first novel debuts this fall. She lives with her kitten, Zoey overlooking the waterfront in beautiful Dartmouth, Nova Scotia - also known as the “City of Lakes”.

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