Are Onions Keto-Friendly? (& Substitutes)

Photo of author
Last Updated On

Vegetables are often good for ketogenic diets but there are exceptions. Find out whether onions are keto-friendly and what the best types are.

100 grams of raw white onions contain around 7.6 grams of net carbohydrates (total carbs minus fiber).

In amounts of this, onions are somewhat high in carbs and in turn, not that keto-friendly.

That being said, most people will use onions as an ingredient in dishes.

You can likely eat onions in smaller amounts while staying in ketosis but you may have to pay attention to the other things you eat.

Another option you have is to choose one of the more keto-friendly onion types or substitutes available.

How many carbs there are in onions

How many carbs there are in onions plays a big role in whether this vegetable will be keto-friendly for you and in what amounts.

One medium white onion is about 100 grams and contains the following amounts of carbs (1):

  • Total carbs: 9.3 grams
  • Of which fiber: 1.7 grams
  • Net carbs: 7.6 grams

There are definitely foods that are higher in carbs too.

However, the 7.6 grams of net carbs in 100 grams of onions in combination with the rest of your diet would likely be enough to kick you out of ketosis.

For this reason, it is fair to say that onions are typically not that keto-friendly.

One ounce of onion is about 28 grams and contains the following amounts of carbs:

  • Total carbs: 2.6 grams
  • Of which fiber: 0.5 grams
  • Net carbs: 2.1 grams

As you can expect, eating smaller amounts of onions will also make it so you consume fewer carbohydrates. In turn, your chances of staying in ketosis go up.

So since recipes often implement onions in only small amounts, you can likely eat these on a ketogenic diet.

That being said, if you consider this, you do want to be careful about your portions and the other foods in your diet.

Other nutrition information onions

Ketogenic diets require you to pay attention to carb intake but that is not the only thing that matters.

Other nutrients like fats, proteins, vitamins, and minerals also play a role in whether you will stay in ketosis and how good your general health will be.

100 grams of raw onions contain the following nutrients (1):

  • Calories: 40
  • Protein: 1.1 grams
  • Carbs: 9.3 grams
  • Part of the carbs that is fiber: 1.7 grams
  • Fat: 0.1 grams
  • Vitamin C: 12% of the DV (Daily Value)
  • Vitamin B6: 6% of the DV
  • Manganese: 6% of the DV
  • Folate: 5% of the DV
  • Potassium: 4% of the DV

And some other vitamins and minerals in smaller amounts.

The extra nutrients in onions are welcome but not that impressive either. You should be able to find many foods that are more nutritious but lower in carbs than onions.

If you do decide to add some onions to your ketogenic diet, it will mostly be for the relatively unique taste it offers.

Why onions can sometimes kick you out of ketosis

Whether onions are keto-friendly or not is not just a yes or no answer. The ketogenic diet fundamentals can help you understand why this is and how to avoid eating too much.

Any way of eating where you get and stay in ketosis is a ketogenic diet. Ketosis is a state where you mainly burn fat as fuel (2).

To get into this state you need to keep your carbohydrate consumption low enough. Exactly how low depends on things like your weight, muscle mass, exercise habits, and genes.

This makes reality more complicated but there are still some general guidelines. These guidelines are not perfect but they do help you understand to some extent how many grams of onions you can more or less eat on keto.

A typical recommendation to get into ketosis is to get 55%-60% of your macronutrients from fat, 30%-35% from protein, and 5%-10% from carbohydrates.

This results in being able to eat around 20 to 50 grams of carbs a day for most people.

Something to note is that you typically don’t include the fiber from onions and other foods. Fiber is a category of carbs but your body processes them in different ways.

With this information, you make a rough estimation of how many grams of onions would still fit into your diet without kicking you out of ketosis.

What kinds of onions are keto-friendly?

There are different kinds of onions with slightly different amounts of carbs. You may wonder if there are ones that are more keto-friendly than the regular white ones.

The short answer is that yellow onions tend to be the most keto-friendly type but that even these are still not that keto-friendly.

You can find the more detailed amounts of carbs in different kinds of onions below.

There are also some onion-like substitutes that are lower in carbs than regular onions. You can find these in a later section.

Are purple and red onions keto-friendly?

There is also something called a purple aka red onion. 100 grams of these contain the following amounts of carbs (3):

  • Total carbs: 9.9 grams
  • Of which fiber: 2.2 grams
  • Net carbs: 7.7 grams

This is basically the same as the 7.6 grams of net carbs in white onions. In turn, the same principles apply.

The number of carbs in purple and red onions is typically not that keto-friendly. At the same time, you could still stay in ketosis if you only implement small amounts.

Are yellow onions keto-friendly?

100 grams of yellow onions contain the following amounts of carbs (4):

  • Total carbs: 8.6 grams
  • Of which fiber: 1.9 grams
  • Net carbs: 6.7 grams

Yellow onions are somewhat lower in carbs than white, purple, and red onions. This also makes them slightly better for ketogenic diets.

At the same time, the net carbs above are still somewhat high. In turn, yellow onions are still not that keto-friendly.

Again, you can likely still consume small amounts in a keto-friendly way.

Are sauteed onions keto?

Unfortunately, I did not find a good nutrition data source for sauteed white onions.

That being said, the USDA does have a mention of sauteed yellow onions. 100 grams of these contain the following amounts of carbs (5):

  • Total carbs: 7.9 grams
  • Of which fiber: 1.7 grams
  • Net carbs: 6.2 grams

Surprisingly enough, the nutrition source implies that sauteed onions are slightly lower in carbs and in turn a bit more keto-friendly than the regular raw version.

Is onion powder keto?

Onion powder is basically dried onion that is ground down into a powder. 100 grams of this contain the following amounts of carbs (6):

  • Total carbs: 79.1 grams
  • Of which fiber: 15.2 grams
  • Net carbs: 63.9 grams

From the perspective of 100 grams, onion powder is definitely not keto-friendly.

That being said, most people do not consume onion powder in these big amounts. You may be able to fit small amounts into your ketogenic diet anyway.

Substitutes for onions on keto

You typically use onions to add a bit of extra taste to recipes. Luckily, you don’t have to give this up when following a ketogenic diet.

There are a few substitutes that are not entirely the same in terms of taste but do contain fewer carbs than onions. In turn, they could be better choices.

The numbers next to these substitutes are the amounts of net carbohydrates per 100 grams (7, 8, 9, 10):

  • Celery: 1.8 grams of net carbs
  • Chives: 1.9 grams of net carbs
  • Fennel: 4.2 grams of net carbs
  • Scallions: 4.7 grams of net carbs

These substitutes are a good amount more keto-friendly than onions but they do still contain carbohydrates.

You may still need to pay some extra attention to the amounts you eat to stay in ketosis.

Why do you follow a ketogenic diet?

By now it should be clear that onions can kick you out of ketosis after already eating a decent number of carbohydrates.

How much of a problem this is depends on your goals with following a ketogenic diet.

For example, there are people who need/want to stay in strict ketosis 24/7. If you are in this category you want to be very careful with how many grams of onions you eat and potentially even stay away from them.

On the flip side, onions can still be good for weight loss and health even if they raise your carbohydrate consumption too much to stay in ketosis.

A keto diet can be helpful for losing weight and getting healthier but there are typically other ways to achieve these things too.

  • Total carbs: 9.3 grams
  • Of which fiber: 1.7 grams
  • Net carbs: 7.6 grams

Related posts:

Will onions kick you out of ketosis?

Whether onions will kick you out of ketosis depends on your portion, what you already ate, and how many carbs your body can take. That being said, bigger portions of onions will likely kick you out of ketosis.

Are onions high in carbs?

100 grams of raw white onions contain around 9.3 grams of carbohydrates (including 1.7 grams of fiber). In turn, you can say that onions are reasonably high in carbs.

Photo of author


Matt Claes founded Weight Loss Made Practical to help people get in shape and stay there after losing 37 pounds and learning the best of the best about weight loss, health, and longevity for over 4 years. Over these years he has become an expert in nutrition, exercise, and other physical health aspects.