Are Onions Keto? How Much Can You Have?

Onions are a staple of nearly every diet, but keto dieters commonly ask: are onions keto? As non-leafy vegetables, they do contain some carbohydrates that might not make them appropriate for every keto diet. However, many keto dieters work onion into their daily meals without any issue, and, for the most part, onions are keto-friendly if used correctly.

Below, we’ll be discussing onions on a keto diet further, including how you can use them to help remain in ketosis, which onions are best for a keto diet, and some alternatives you can use in your cooking to deliver the flavor and health benefits of onions without as many carbs. Let’s get started!

How Much Onion Can You Eat on a Keto Diet?

KetoConnect verdict: We give onions a keto-friendly rating of ⭐⭐⭐(out of 5)

The answer to the question, are onions keto, depends on a few things, primarily how much you intend to use. Onions are typically considered “keto-friendly,” but they aren’t suitable in large volumes. All types of onions contain carbohydrates. The starches and sugars in onions could potentially push you over your daily net carb limit and bring you out of ketosis.

Most keto dieters aim to eat between 20 and 50 grams of carbs daily, which would be very challenging to reach with just onions. Other people on a keto diet restrict themselves to 25g or fewer, sometimes aiming for as close to 0g of carbs as possible.

While onions likely wouldn’t threaten your ketogenic state if you eat fewer than 50g of carbs, half an onion in a dish might add enough carbs to put you over your limit if you aim to eat under 5g or even 10g of carbs per day.

How Many Net Carbs Are In an Onion?

Most onion varieties contain between 10 and 15g of carbohydrates per one medium sized onion or 9 to 10g per 100g of onion. A few grams of dietary fiber bring the total net carbs to between 8 and 12g, depending on the type of onion.

What Kinds of Onions Are Most Keto Friendly?

The number of carbohydrates you’ll consume when you eat onion depends on the type you use in your meal. Yellow onions are the best low carb option, as they have the lowest amount of sugar and total carbohydrates.

A cup of chopped yellow onion contains around 7g of carbohydrates and just 1g of dietary fiber. Of the 6 grams of net carbs in a yellow onion, just 1g comes from sugar. This makes yellow onions keto friendly compared to other varieties.

Red onions contain approximately 15g of carbs per cup of chopped onion and around 12g of net carbs. Of these net carbs, about half come from sugars.

White onions contain about 15g of carbohydrates per cup and 3g of dietary fiber. That brings the total net carbs to 12g with 7g of sugar per cup of chopped white onion.

As you can probably guess, sweet onions — sometimes called Vidalia onions — are usually considered the worst option for keto dieters. They contain 12g of carbs per cup, around 1g of dietary fiber, and the most sugar of any onion: 8g.

The bottom line: if you’re looking to work onion into your keto diet, your best option is to avoid sweet onions and white onions as much as possible and favor yellow onions for their lower sugar and total carbohydrate content.

Is Onion Powder or Dried Onion OK for Keto?

Some people believe that dried onion flakes and onion powder are more low carb and keto friendly than regular onion. Unfortunately, this is inaccurate. Dried onion and onion powder both have just as many carbohydrates and sugars as normal onion.

Most sources confirm that you need about a tablespoon of either to get the flavor of a full onion. The nutrition facts of dried forms of onion demonstrate that the total carb content, the net carbs, and the grams of sugar are all about equal when you substitute powder or dried onion for raw onion.

One great thing about dried onion though is a little goes a long way as far as flavor is concerned. If you add between 1/4 and 1/2 teaspoon of onion to a dish, you will taste the effect while only consuming around 3g of carbs. 

And luckily, the health benefits of onions — like abundant antioxidants — can still be enjoyed if you use dried or powdered onion.

How Can You Use Onions to Help Stay in Ketosis?

While onions might not be the perfect low carb food for keto dieters, you can actually use them to stay in ketosis if you include them in your diet sparingly. There are a few things you need to do to use onions on a keto diet successfully.

First, choose yellow onions over other varieties in your keto meal as often as possible. These have the fewest net carbs and the lowest amount of sugar per serving.

Second, use them to add flavor to your food instead of sugar or sugary condiments. We all crave delicious and flavorful food, and we sometimes use sugar or sauces like ketchup, BBQ sauce, and dressings that add flavor at the expense of carbohydrates. Onions contain carbs and sugars but are relatively low in both, so they can pack in tons of flavor and help you avoid other flavorful ingredients that are even worse for keto.

Finally, use onions sparingly in your keto diet. The good thing about onions is that a little goes a long way. You probably don’t need a cup of onion in a meal to get a bold flavor, so cutting that amount down to a quarter cup will deliver some relatively low carb flavor that won’t bring you out of ketosis.

What Are Some Keto Alternatives for Onions?

If you’re a keto dieter who drops out of keto after consuming very few carbs and works tirelessly to keep your carbohydrate consumption as low as possible, onions might not work in your diet. Luckily, there are some flavorful alternatives that belong to the allium family that you can use to make your keto dishes more exciting and bold without adding too many net carbs.

Garlic

Garlic is one of the best low carb alternatives to onions for a keto diet. Garlic is full of flavor, and while it tastes distinctly different from onion, it often provides the same bold taste that we crave in our meals. There are also various health benefits to eating garlic, including a boosted immune system.

One tablespoon of garlic is usually much more than sufficient to flavor an entire keto meal, and it only contains 3g of carbs and about 1g of sugar. Given the low net carb content, most keto dieters can use about as much garlic as they can eat in a day without worrying about it pushing them out of ketosis.

Shallots

Shallots are a type of onion that also belong to the allium family. They do contain quite a few carbohydrates, but most keto dieters use less shallot in a recipe than they would raw onion. The taste is a bit bolder, so you will likely use a smaller portion of shallot that contains fewer net carbs overall.

A 100g serving of shallots — which is a lot! — contains around 17g of total carbohydrates, including 3g of dietary fiber and 8g of sugar. This serving is around the same as white onions, but the total sugars you’ll be adding to your dish will be lower because you’re more likely to use less when you cook your keto meal.

Green Onions

Green onions — also called scallions — also belong to the allium family, so they provide the same type of oniony flavor to recipes that call for them. Like shallots, most people use smaller portions of green onions per keto meal, as the taste is more robust than that of an onion.

For a 100g or 1-cup serving, you can expect green onions to provide around 7g of carbohydrates, 2.5g of dietary fiber, and just 2g of sugar. Most dishes will call for far smaller of a serving of scallions, so the carb content of what you actually consume will very likely be minimal.

Keto Recipes Using Onions

Onions are a great way to add flavor to your recipes. It’s important to keep an eye on just how much onion you are using in order to ensure you’re staying under your daily carb limits. Check out some of our favorite recipes that use just the right amount of onion!

• Keto Onion Rings – What better way to get that delicious onion flavor than with a childhood favorite?
• Keto Big Mac Salad – Just like the burger, but healthier and maybe even tastier.
• Keto Philly Cheesesteak Casserole – A Philly cheesesteak is one of the best foods ever invented. This casserole brings all the flavor without the carbs.
• Keto Taco Salad Casserole – If you’re missing your taco salads since starting keto, give this recipe a try.
• Keto Nachos – For those nights where you don’t feel like spending much time cooking but you still want a delicious dinner.

Wrapping Up: Are Onions Keto Friendly?

Onions are flavorful and can add depth to just about any dish. Plus, they contain vitamins and minerals, so many keto dieters look beyond the carb content to enjoy the many health benefits of onions. However, they do contain carbohydrates and a minimal amount of dietary fiber. Most concerning for keto dieters is the sugar content in onions. In substantial amounts, onions could cause a spike in blood sugar levels and bring you out of ketosis.

With that being said, anyone can work onions into their keto diet as long as they count their carbohydrates and make sure their consumption is under the limit for the day. If you aim for under 50g of carbs per day, onions will contribute very little toward that number. If your goal is as few carbs as possible, you should plan to use onions sparingly to add a bit of flavor to your dishes but without introducing too many net carbs.

Read our other articles on foods that people have questions about on a ketogenic diet, including carrots, beets, rice, honey, radishes, popcorn, chickpeas and mushrooms.

Onions can be great for keto if you use them in place of sugar or carb-heavy sauces or condiments for flavor. For the lowest carb content and massive flavor in your keto dishes, you can consider substituting other members of the allium family for onions, including garlic, shallots, and scallions.

Written by

Expert Fact Checker