Home  /  All  /  Nutrition

Everything You Need to Know About Onions on Keto

Written by
  Published on February 25th, 2022
  Reading time: 3 minutes
  Last modified July 17th, 2023
onions on keto

Onions are a commonly consumed vegetable in many dishes across the world. Their unique flavor adds depth to a variety of meals from steak to salad. Since many vegetables are excluded from the ketogenic diet (since they are high in carbohydrates), you may ask yourself if onions are keto. The answer is more complicated than yes or no, so let’s dive into it.

Onion Varieties

There are several different types of onions that vary in color, flavor, and nutritional profile. Let’s go over the four most common types of onions, what distinguishes them, and how they are best consumed. 

Yellow onions are some of the most common onions. Because they caramelize well, they tend to be used for cooking. They are perfect for topping a steak or adding to a casserole. 

As the name suggests, sweet onions are a popular onion that has a hint of sweetness to it. These are typically used in salads or as a part of relishes. 

While yellow and sweet onions have a yellow-ish white tint, red onions are obviously red in color. These onions have a strong flavor and pack a  more peppery punch. These onions are perfect for frilling, pickling, or garnishing a salad. 

Lastly, white onions are a crunchy variety with a less pungent aftertaste than some of their counterparts. These onions are commonly found in Mexican cuisine (i.e. salsa, guacamole, or tacos), but are also commonly used in barbeque. 

Benefits of Onions

Besides providing a delicious flavor, onions actually pack multiple health benefits. Onions contain micronutrients such as vitamin B, vitamin C, and potassium. They are all packed full of antioxidants that may help reduce inflammation and lower the risk of cardiovascular disease and cancer. [1]

Onions are rich in the antioxidant quercetin, which has been shown to improve blood pressure levels in clinical trials. [2] 

Additionally, research has shown that the consumption of raw onions may help individuals with PCOS lower cholesterol levels. [3]

White and red onions

Onion Nutrition Facts

There are many different varieties of onions but for these purposes, we will be breaking down the nutrition facts of the three most common onion varieties: sweet onions, yellow onions, white onions, and red onions. 

Sweet Onions [4]

Serving: 100g

Calories: 32

Fat: 0.08g

Carbs: 7.55g

Fiber: 0.9g

Protein: 0.8g

Yellow Onions [5]

Serving: 100g

Calories: 38

Fat: 0.05g

Carbs: 8.61g

Fiber: 2.71g

Protein: 0.83g

White Onions [6]

Serving: 100g

Calories: 36

Fat: 0.13g

Carbs: 7.68g

Fiber: 1.2g

Protein: 0.89g

Red Onions [7]

Serving: 100g

Calories: 44

Fat: 0.1g

Carbs: 9.93g

Fiber: 3.97g

Protein: 0.94g


Onions & Inflammation

Onions do contain nutrients that may help reduce inflammation in the general population. That being said, though, onions can be a highly triggering food for individuals with food sensitivities. Onions are considered high-FODMAP foods since they have a high concentration of fructans (oligosaccharides).  Therefore, onions should be avoided in individuals with IBS, Chron’s disease, or other digestive issues.  

Are Onions Keto?

If you don’t have a sensitivity to onions, you may be wondering if they are keto or not. The answer is they can be, in moderation. Sweet onions contain 6.65g of net carbs per 100g. Yellow onions have 5.9g, white onions have 6.48g, and red onions have 5.96g of net carbs per 100g. 

On a ketogenic diet that limits carbohydrate consumption to 5% of total daily calories, the average person can only consume 20-25g of net carbs a day. Unfortunately, a 100g serving of onions (of any variety) is over a quarter of your total daily calories. 

That doesn’t mean that you have to completely cut onions out of your diet. Instead, practice consuming them in small quantities. A 100g serving is about ⅔ cup of chopped onion. Since this is a pretty large serving for onions, it should be easy to reduce the serving size consumed to limit the total number of carbohydrates being consumed. Try sticking to ¼ – ⅓ cup servings of onions. 

Since yellow onions are the lowest in net carbohydrates, try swapping those out for sweet onions or red onions otherwise used in your diet to limit carb consumption.

Delicious Keto Recipes With Onions

Are you looking to incorporate more onions on your keto diet? Try one of these tasty recipes! 

Do You Enjoy Onions On Keto?

Comment below and share your favorite way to include onions in your diet!

At ketogenic.com, we are committed to supporting, inspiring, and educating people on the benefits of living a ketogenic lifestyle. We do this by bringing together the top researchers, practitioners, and thought-leaders who provide resources, experience, and awareness associated around the Ketogenic diet. Utilizing the latest cutting-edge research along with practical experience, the team at ketogenic.com aims to foster awareness, understanding, and connectedness in helping others optimize their life on a ketogenic diet.



Sidhu JS, Ali M, Al-Rashdan A, Ahmed N. Onion (Allium cepa L.) is potentially a good source of important antioxidants.J Food Sci Technol. 2019 Apr;56(4):1811-1819. doi: 10.1007/s13197-019-03625-9. Epub 2019 Feb 13. PMID: 30996417; PMCID: PMC6443770.


Brüll V, Burak C, Stoffel-Wagner B, Wolffram S, Nickenig G, Müller C, Langguth P, Alteheld B, Fimmers R, Naaf S, Zimmermann BF, Stehle P, Egert S. Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial. Br J Nutr. 2015 Oct 28;114(8):1263-77. doi: 10.1017/S0007114515002950. Epub 2015 Sep 2. PMID: 26328470; PMCID: PMC4594049.


Ebrahimi-Mamaghani M, Saghafi-Asl M, Pirouzpanah S, Asghari-Jafarabadi M. Effects of raw red onion consumption on metabolic features in overweight or obese women with polycystic ovary syndrome: a randomized controlled clinical trial. J Obstet Gynaecol Res. 2014 Apr;40(4):1067-76. doi: 10.1111/jog.12311. Epub 2014 Mar 10. PMID: 24612081.


Onions, sweet, raw. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/170008/nutrients


Onions, yellow, raw. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/790646/nutrients


Onions, white, raw. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/1104962/nutrients


Onions, red, raw. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/790577/nutrients


  1. Douglas Legvold says:

    I use red onions to add flavor. One onion will last over a month in my fridge. I’ll slice off a thin round or half of a round and chop it up and add it to a pound of ground beef or a grilled chicken salad with olive oil and ACV dressing. Yum!

Leave a Comment

Your email address will not be published. Required fields are marked *

As a Member, you get instant access to personalized meal plans, exclusive videos & articles, discounts, a 1 on 1 Coaching Session, and so much more. As a member, you join our mission of empowering 1,000,000 people to positively change their lives throughout the world. Get started today.


A Great Deal
$ 19
99 /month
  • 7-Day Free Trial
  • Cancel Anytime


3 Months Free
$ 179
  • 3 Months Free
  • Cancel Anytime


Membership for Life
$ 349
  • Lifetime Access
  • Limited Availability