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Are Onions Keto-Friendly?

Onion on a kitchen counter

As we embark on this exploration of the gray areas, 'Are Onions Keto-Friendly?' we find the response sitting comfortably in a realm of 'Yes, but…'.

Onions, essential in countless recipes for their unique flavor, do have more carbs than some other veggies. However, they can still fit into a keto diet when you manage portions carefully. Just be mindful of your daily carb intake, and you can enjoy the rich taste onions add to your meals without tipping the carb scale.


  • Onions can fit into a keto diet, but their high carb content makes portion control crucial.
  • While onions offer health benefits, their carb count can potentially lead to the onset of 'keto flu.'
  • Irregulated consumption risks disrupting ketosis, making your ketogenic journey a precarious one.

Are Onions Keto-Friendly?

Yes, onions are keto-friendly in moderation. With 7.64 grams of net carbs per 100 grams, they can be included in a keto diet as long as you keep an eye on your overall carb intake for the day. It's all about balancing your meals and ensuring you stay within your daily carb limits.

Given this low carb threshold in a ketogenic diet, even seemingly small amounts, such as those found in onions, can quickly pile up and potentially jeopardize your state of ketosis. For example, a small-medium onion (around 110 grams) would almost reach this limit, with around 8.40 grams of net carbs.

This doesn't mean you can't have onions on a keto diet, but it does mean you have to be careful with how much you use. A little bit of chopped onion in your keto dish should be fine and fit into your daily carb limit. But, if you use a lot of onions as a main ingredient, it might use up too much of your carb allowance.

Can You Have Onions on a Strict Keto Diet?

Yes, you can have onions on a strict keto diet, but in very small amounts. Since onions have carbs, you'll need to use them sparingly to stay within your strict daily carb limits. Think of adding just a little for flavor, not as the main ingredient of your meal.

A smart way to enjoy onions on a strict keto diet is to carefully measure how much you use. Instead of using a whole onion, just use a few slices or dices. Finely chopping them and spreading them out in your dish can add flavor without adding too many carbs.

Also, using apps or tools to track your carbs can really help. By keeping track of what you eat every day, you can make sure you stay within your carb limit. This way, you can still enjoy the taste of onions in your meals without worrying about going over your carb budget.

Carbs in Onions

Onions, per 100 grams, pack a total carb content of 9.34 grams. When delving deeper, we find that they contain 1.7g of fiber per 100 grams. Subtracting dietary fiber from the total carbs gives us the net carbs, which is the digestible carbohydrate content that directly impacts your blood sugar levels. So, by doing the simple math, onions have 7.64g of net carbs per 100g.

Onion Nutrition Facts

Onions, in a 100g serving, are loaded with nutrients that are great for our health when eaten in moderation. They have both big and small nutrients. Starting with the big ones, onions have about 7.64g of net carbs and 1.7g of dietary fiber, making for a well-rounded carb profile.

When we dive into the smaller nutrients, onions pack a punch with 4.0mg of Sodium and 146.0mg of Potassium, crucial for keeping our body's fluids in balance. They also bring a good amount of important minerals to the table, like 10.0mg of Magnesium, 23.0mg of Calcium, 0.21mg of Iron, and 0.17mg of Zinc, all key players in various bodily functions.

On top of that, onions are a great source of vitamins, especially Vitamin C (7.4mg) which boosts immunity, and Vitamin B-6 (0.12mg) important for brain health. They also contain beta-carotene (1.0ug) that our body can easily use, and the essential amino acid Lysine (0.04g).

With an energy value of 40.0kcal, onions are not just flavorful but also a smart choice for a balanced diet.

Nutrient NameAmount and Unit per 100g
Net Carbs7.64g
Carbohydrate, by difference9.34g
Fiber, total dietary1.7g
Total fats0.1g
Sodium, Na4.0mg
Potassium, K146.0mg
Magnesium, Mg10.0mg
Calcium, Ca23.0mg
Vitamin B-60.12mg
Vitamin C, total ascorbic acid7.4mg
Vitamin E (alpha-tocopherol)0.02mg
Vitamin K10.4ug
Copper, Cu0.04mg
Iron, Fe0.21mg
Phosphorus, P29.0mg
Selenium, Se0.5ug
Zinc, Zn0.17mg
Fluoride, F1.1ug
Lutein + zeaxanthin4.0ug
Manganese, Mn0.13mg
Pantothenic acid0.12mg
Folate, total19.0ug
Choline, total6.1mg
Aspartic acid0.09g
Glutamic acid0.26g
Fatty acids, total saturated0.04g
Fatty acids, total monounsaturated0.01g
Fatty acids, total polyunsaturated0.02g
Nutritional data is sourced from the US Department of Agriculture's FoodData Central system. Please see Cast Iron Keto's editorial and research standards for more information.

Health Implications of Onions on a Keto Diet

Onions are not just about carbs; they are also loaded with beneficial nutrients and compounds. They offer a source of Vitamin C, vital for skin health and immune function, and Vitamin B6, crucial for brain development and function. They also deliver a healthy dose of fiber, contributing to digestive health.

Adding to this, onions have potent antioxidant and anti-inflammatory properties, attributed mainly to their rich flavonoid content, particularly quercetin. These antioxidants can potentially protect against cellular damage and inflammation.

How to Limit Onions in Your Keto Meal Plan

One strategy for onion lovers is to have them thinly sliced, sautéed in a high-fat, keto-friendly oil, like coconut oil, and then use them sparingly to top a keto steak or garnish a green salad.

Another option is to pair onions with other low-carb vegetables. For instance, in a lavish keto salad, you could balance your onion addition with a broad array of low-carb vegetables like leafy greens, cucumbers, or radishes. This way, you can continue to enjoy the diverse flavors onion adds to salads while controlling your overall carb load.

Keto-Compatible Alternatives for Onions

  • Scallions: One such potential substitute is scallions, also known as green onions. They can offer similar flavor notes but with less impact on your carb intake. A 100-gram serving boasts just 4.37 grams of net carbs - quite a reduction compared to the same serving size of onions.
  • Chives are another keto-compatible option. Lower yet in carbs, 100 grams of chives have a minimal 2.02 grams of net carbs. Used often as a garnish, their slight onion-like flavor can enhance dishes without burdening your carb count.
  • Shallots provide another flavorful alternative. While their net carb count of 14.8 grams per 100 grams is higher than that of onions, their more intense flavor means that just a small amount offers a similar taste.

For example, a keto stir-fry could switch out regular onion with a sprinkling of finely chopped scallions or a small amount of diced shallots. On the other hand, a garnish of fresh chives over your keto salmon dish could hit those onion-flavored notes without pushing the carb limit.

Keto Friendly Onions List

Let's analyze some of the most popular keto-friendly onions that you'll find in most recipes (including ours) and how you can add them to your keto diet plan.

Pearl Onions

"Are Pearl onions keto?" - They are indeed keto-friendly when consumed in moderation. These small, sweet onions pack a flavorful punch with a relatively low carb count. A half-cup serving of pearl onions contains about 6 grams of carbohydrates and 1 gram of fiber, netting 5 grams of carbs.

Their size and sweetness make them an excellent addition to dishes, adding depth and flavor without a significant carb increase, making them a suitable choice for those adhering to a ketogenic lifestyle.

Yellow Onions

Yellow onions are keto-friendly in moderation. While they are higher in carbs compared to some other vegetables, they can still fit into a keto diet when used judiciously. A half-cup serving of chopped yellow onion contains about 6 grams of carbohydrates and 1 gram of fiber, netting around 5 grams of net carbs.

Red Onions

If you were wondering, "Are red onions keto?" we have good news. Red and purple onions are keto-friendly when consumed in moderation, similar to yellow onions. They contain approximately the same amount of carbohydrates—about 6 grams per half-cup serving, with 1 gram of fiber, resulting in 5 grams of net carbs. Given their rich, vibrant flavor and color, they can enhance a variety of dishes without significantly impacting your carb intake, as long as you keep portion sizes in check.

Green Onions

Yes, green onions (also known as scallions) are very keto-friendly. They contain even fewer carbs than their yellow, red, or purple counterparts. A half-cup of chopped green onions has about 1.2 grams of net carbs, making them an excellent choice for adding flavor and nutrition to your keto meals without significantly impacting your carb count.

Concluding Thoughts on Onions and Keto

We've looked at the benefits and the hurdles, plus shared some clever ways to enjoy onions without going overboard on carbs. Despite their nutritional perks, like Vitamin C, Vitamin B6, and anti-inflammatory benefits, we can't ignore their carbs when we're trying to stay in ketosis.

But this doesn't mean onions are off the table forever. You can still enjoy them by using small amounts, mixing them with low-carb veggies, trying dried or powdered onions, or just sprinkling them as a garnish.

Looking for alternatives? Scallions, chives, and shallots can step in to keep that onion flavor in your keto-friendly dishes. It's all about experimenting to find what works for you and your diet.

In the end, although onions and a strict keto diet aren't a perfect match, they don't have to be strangers. With smart planning and some kitchen creativity, you can still indulge in that onion taste without messing with your carb count..

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Cast Iron Keto's Editorial and Research Standards

Certain rare or exotic food items may not have nutritional profiles in the FoodData Central database. If an exact match is not found in the FoodData Central database, then, the Cast Iron Keto team utilizes a three-prong approach to provide readers with the closest relevant nutritional data, where possible.

First, in the event that nutritional profiles for a rare or exotic food item is not available in the FoodData Central database, we investigate alternative names for that particular food item and use that data, when possible. Second, in cases where no alternate names exist, Cast Iron Keto will use nutritional data for a close relative or similar food item. Finally, if no close relatives or similar items exist, we refrain from publishing nutrient data tables.

When making dietary or health decisions based on FoodData Central's data, we suggest readers consult with a nutritionist or other health experts, particularly if the food in question has a significant role in your diet or if you are using the food item to treat any health disorder(s).

Furthermore, it is important to note that even if a close relative or similar item is used to approximate the nutritional data, different food items can have varying levels of nutrients due to factors such as soil quality, farming practices, and regional differences.


The information on this website is only intended to be general summary information for public use, designed for educational purposes only and is not engaged in rendering medical advice or professional services. This information does not replace written law or regulations, nor does it replace professional medical advice, diagnosis, or treatment. If you have questions about a medical condition or are seeking to evaluate the health merits of certain food items for the treatment of any medical condition, you should seek the advice of a doctor or other qualified health professionals.

The views expressed at, or through, Cast Iron Keto are for informational purposes only. Cast Iron Keto cannot guarantee the validity of the information found here. While we use reasonable efforts to include accurate and up-to-date information, we make no warranties as to the accuracy of the content and assume no liability or responsibility for any errors or omissions in the content. All liability with respect to actions taken or not taken based on the contents of this website are hereby expressly disclaimed. The content on this posting is provided "as is;" no representations are made that the content is error-free.

Frequently Asked Questions

Yes, onions can be included in a keto diet, but due to their relatively higher carbohydrate content, they must be consumed in moderation and with strict portion control.

grams of onions contain approximately 9 grams of carbs. Due to this high carb content, onions can potentially disrupt ketosis if consumed in large amounts.

Excessive onion consumption might tip the balance of your carb intake and could potentially trigger the 'keto flu,' a collection of symptoms that some people experience when starting a ketogenic diet.

Yes, other vegetables like scallions, chives, and shallots can be used as keto-friendly alternatives due to their lower carb content and similar flavor profile.