Are Onions Keto-Friendly?

Author Image

Written by Bridget Nalwoga, Certified Nutritionist and medically reviewed by Abby Courtenay

Imge of Are Onions Keto-Friendly?



Many people eat onions in some form every single day. They are arguably the most used food item in cooking. Whether it is fast food, fine cuisine, or a salad, they are there.

In addition to their wonderful taste, they are incredibly nutritious, affordable, and have a good shelf life. Considering all these reasons, it is no surprise that they are ever present in most people’s diet. 

Onions are a non-starchy vegetable, which would usually qualify them for keto — but in this case, it is not that simple. In this article, we look at onion nutrition and determine whether it is suitable for the ketogenic diet.  

What is an onion?

The onion is a bulb vegetable cultivated for its pungent flavor. Its origin remains unclear as it has been a part of almost all cultures for centuries. Some historians believe that it may have originated from central Asia, particularly Pakistan. 

These vegetables are mostly used to boost flavor in savory dishes. They are commonly sauteed in oil to impart their flavor to a dish. They can also be sliced up and eaten raw in salads. 

They are mostly used fresh, but are also available frozen, canned, caramelized, pickled, and powdered.

Similar to any vegetable, they have a rich nutrient composition. 


Onion nutrition facts

Onions are almost 90% water. The other 10% is mostly carbohydrates and a variety of micronutrients and phytochemicals.

If you pay close attention to the taste of an onion, you will notice a slight sweetness to it. Unfortunately on keto, that is not good news. This is because sweetness usually means more sugar, and more sugar means more net carbohydrates. 

Serving Size: 1 raw red onion (197 g)

  • Calories: 83 kcal
  • Fat: 0.2 g
  • Net carbs: 11.8 g
  • Total carbs: 19.6 g
  • Fiber: 7.8 g
  • Protein: 1.9 g

Here you can see that onions do have carbs. But is the carbohydrate amount too high for ketosis?



Can you eat onions on keto?

Yes, it is OK to eat onions on keto. If you tread with caution. 

You can use them in cooking on keto as the carbs will be split between everyone sharing the meal. When cooking for one, use a portion enough for one serving.

The problem is with dishes that call for raw onions. Such dishes tend to use sweet varieties and usually require more per serving. 

If you are just starting your keto journey, it is best to avoid raw onions for a while until your body is accustomed to being in ketosis. If you have been on keto for a while, you can eat them as long as you can practice good portion control. 

11.8 g of net carbohydrates may seem high per serving, but remember onions make up such a small part of any dish.

How many onions on keto can you eat?

Unless you are the biggest fan of onions in the world, there is usually no need to control portions when it comes to cooking with them. 

As part of a meal, one medium-sized onion (about 200 g) is usually adequate for cooking. Remember, it is split across all the servings that will come from that dish. If a dish makes 4 servings, each serving will have 25 g. That is only 2.9 g of net carbohydrates for each person.

When eaten raw, some portion control will be required as a serving can call for up to 100 g, which will give you closer to 6 g carbs. 

If you like your raw dishes like guacamole with lots of onions, it is advisable to portion them out before eating. 

What is the best type of onions to eat on keto?

Onions are classified according to their appearance, more specifically color. The four most common types are:

  • Red or purple onions. This type has the mildest flavor, making them great for raw dishes like salads. 
  • White. These have the strongest and most pungent flavor and are commonly used in Mexican dishes like guacamole and salsa. 
  • Yellow. The yellow variety also has a strong flavor, making it great for cooked dishes like stews, soups, and roasts. 
  • Sweet. These are not pungent but still have a wonderful ‘oniony’ taste making them ideal for raw dishes. 
  • Green onions, also known as scallions. These are harvested before bulbing. Since they are immature, they have the least simple carbohydrates and therefore net carbs. 

Take a look at the carb count for each kind of onion below.


Type of onion Net carbohydrates per 100 grams
 Red / purple  5.9 g
 White  6.5 g
 Yellow  6.7 g
 Sweet  6.7 g
 Green / spring onions / scallions  4.7 g

Among these types, it is clear that scallions are the lowest carb onion and best for keto. However, do not feel like you need to use scallions all the time. 

Scallions do not give the same flavor in cooking as the other types. The sacrifice in taste is not worth the slight carb difference. Unless, of course, you do not mind. Otherwise, go with the type that best suits your cooking needs. 

Onions can also be grouped according to how they are processed:

  • Pickled. Even though these have sugar in them, you can fit them into a ketogenic diet. If you are using 3 to 5 rings to top a salad, great. You however cannot have a bunch as a snack. 
  • Powder. After drying, all nutrients go up (except water, of course!). Onion powder, therefore, has more carbs. The good news is that powder is used in very small quantities, so the carb content will be low when used in cooking. 
  • Caramelized. When a food is caramelized, it loses water and volume. This means that a smaller portion caramelized will contain the same amount of carbs as a bigger portion uncooked or lightly cooked.




What compliments onions on a keto diet?

Using onions on a keto diet is not as complicated as you would think. They go with just about any savory dish, including soups, sauces, grilled and oven-baked dishes, and so on. 

Some of the keto-friendly dishes that feature onions as the star include:

  • Salsa
  • Guacamole
  • Keto onion dip
  • Keto onion sauce
  • Salads 

The most keto-friendly onion, scallions, can be used as a topping for almost any savory dish. They also add an extra kick of flavor and crunch to dishes like omelettes. 

Best way to replace onions in a keto diet

Unfortunately, this vegetable has a very distinct flavor that is nearly impossible to imitate using other ingredients. Shallots are the closest in taste, but they actually have more net carbs (13.6 g / 100 g raw). 

Leeks also have a slight onion taste to them, but again have more net carbohydrates (12.4 g / 100 g raw). 

If you are not looking for the exact taste, here are some keto-friendly onion substitutes that may work for you:

  • Fennel looks like an onion but has a more licorice flavor when raw. It can however give you that same crunch for less net carbs.
  • Celery has a very different flavor, but when diced it can give a similar texture to a raw salad. 

Not all hope is lost though. The lower white portion of scallions is more similar in flavor to the more flavorful onions. Do not discard this bit. Instead, dice it up and use it along with the green leaves for a more intense flavor in your raw dishes. 


FAQs about onions on a keto diet

Still a little confused? We don’t blame you. That was a lot to take in. Below we answer some of the questions you may still have on the subject.

Most French onion soup recipes call for bread. For this reason, the soup is not usually keto-friendly. It can however be modified to make a ketogenic version using keto “bread.”  
Here is a recipe you will love.


  • 3 tablespoons butter
  • 1¼ lb onions, thinly sliced (about 3 large)
  • 1 tablespoon erythritol
  • ¼ teaspoon salt
  • 6 cups beef broth
  • ½ teaspoon dried thyme
  • 2 bay leaves
  • Keto bread


  1. Heat the butter in a pan.
  2. Add the sliced onions and cook them till they soften.
  3. Add the salt and erythritol.
  4. Reduce the heat to low and continue to cook till the slices brown. About 20 minutes.
  5. Add the beef stock, thyme, and bay leaves. Cover and simmer for 30 minutes. 
  6. Preheat your oven to 350 F. 
  7. Toast your keto bread.
  8. Pour the soup into an ovenproof bowl.
  9. Butter the toast and rub some raw garlic on it.
  10. Place one piece of toast in each soup bowl and top with French Gruyere cheese.
  11. Broil in the oven until the cheese is brown.
  12. Serve immediately.

Yes, most onion dip brands are keto-friendly. For example, the Lays French onion dip has only 1 g of net carbohydrates per 2 tablespoon serving. You can also make your own keto-friendly onion dip at home that is not heavily processed or loaded with preservatives. 

The amount of carbohydrates in cooked onions depends on the method of cooking used. Caramelized onions contain 8 to 10 g of net carbs per 100 g. Onion rings (especially when breaded) can have up to 30 g of net carbs per serving. 

Traditional onion rings use bread crumbs and flour which makes them high in carbs. Keto onion rings usually use high-fat flours like coconut and almond flour instead.

While onion rings are high in fat, they are not the best source of fat on any diet. The heat used for deep frying breaks down the healthy components in the oil. Opt for foods like avocado, eggs, and fish for healthier fats.  

Yes, they can help with inflammation. Like any plant food, they are rich in phytochemicals, like sulphur compounds, that can help fight inflammation in the body.  

Yes, you can use onion powder on keto. It is true that after drying, the net carbs of any food go up. In fact, onion powder contains almost 80 g of carbs per 100 g. However, unless you are catering an event you will never need 100 g of this powder. 

Most recipes call for 1 teaspoon. A single teaspoon contains only 1.5 g of net carbohydrates. If you are making multiple servings, that will be further split down. 

So, you can enjoy onion powder on keto in your recipes with no worries. 


Alternative keto vegetable options