Can You Eat Onions on a Keto Diet?

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Onions are the eye watering, a mouth-tingling vegetable that is simply irresistible when added to salads, or meals. Depending on the number of onions you plan to use for the day, and comparing it to your daily carb count, would determine how much of the onion you would be able to consume. There are many varieties of onions to choose from, but are they all keto-friendly? Let’s find out.

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What are Onions?

Onions are a part of the allium family of plants, which also includes chives, garlic, and leeks. These vegetables have potent and pungent flavours, with some medicinal properties. Onions vary in shape, size and colour, the most common types consisting of red, yellow, and white onions. The taste of these vegetables can range from sweet and juicy to sharp and spicy, the unmissable heat that explodes in your mouth after a nibble of a white onion can either be described as painful or beautiful. Slicing onions would instantaneously cause your eyes to fill with water, continuing until you’ve removed the raw onion from your sights. Despite this, onions can also provide potential health benefits, which might include: reducing the risk of several types of cancer, improving mood, and maintaining skin and hair health. But are they low carb though?

How Many Carbs Are in onions?

A single onion weighs around 400 grams, and 400 grams of sautéed onions – which is the equivalent of a large onion – has a whopping 31.4 grams of carbs and only 6.8 grams of fibre! This means that a large onion has 26.6 grams of net carbs, even though that is a lot of carbs, you must ask yourself, who even eats that much onion? 1 large onion weighing about 400 grams would make 4.6 cups of diced onions, which is far too many onions to eat in one sitting.

Even if you were oddly obsessed with the smell, taste and texture of onions, you wouldn’t be eating more than 1/2 a cup of diced onions in any single meal. Half a cup of onions is still a lot of onions and will have a total of 2.68 net carbs.

With those figures in mind, you might choose to sauté your 12 cup onions in butter as a base for your meals, which seems more doable while still hitting your carb targets.

Are all Onions Low Carb?

Onions are normally considered keto-friendly, but they aren’t suitable in large quantities. All types of onions contain carbs, the starches and sugars present in the onions could potentially force you over the edge of your daily net carb limit, potentially bringing you out of ketosis. Below are a list of types of onions:

  • Green Onion
  • Red Onion
  • Pearl Onion
  • Shallots

Green Onion

These onions are a great source of vitamin A, one medium green onion (15 grams) contains a total of 1.1 grams of net carbs, and 0.4 grams of fibre, which gives it a grand total of 0.7 grams of net carbs. This means that the green onion is most definitely keto-friendly or low carb. Use them in your soups, or brighten up your salad bowls with these bright green onions for a keto-friendly snack, or evening meal.

Red Onion

These vibrant onions are often used in salads to add some life and texture to the bowl of greens. You can place a ring or two over the top to add a nice touch of colour; choosing to toss a few cubed red onions over your salads could add some depth to it as well. They are usually served raw, but can be sautéed in a little butter or oil.

Red onions contain more carbs than other vegetables, so they might not be considered as keto-friendly, but if you manage to stay within your carb limit you should still be able to enjoy them as a side dish with your dinner. There are 14.5 carbs in a cup of red onions, and with 2.72 grams of fibre, you have a net carb count of 12.23 grams in 1 cup.

Pearl Onion

Pearl onions are small, white onions that are often used in beef stews and other meaty dishes. They have a mild flavour and are usually served whole, cooked in the sauce or juice of a dish. They aren’t as keto friendly when compared to their super low carb cousins – leeks and green onions. However this doesn’t mean that you should completely throw them off your keto diet plan. One cup of pearl onions has 0.3 grams of fat, 15.4 grams of net carbs, 2.6 grams of fibre, and 2.5 grams of protein.


Shallots are a sweeter type of onion, providing a very delicate flavour to your dishes. While they pack some carbs, they’re mostly used as a garnish, so the amount you use would make a normal meals include so little that they’d fit so easily into the keto diet. Shallots are like a combination of their garnish relatives – garlic and onions – they have a distinctive taste that make them popular in keto recipes. One tablespoon of chopped shallots contain 1.4 grams of net carbs. If you were to consume shallots in large quantities you might knock yourself out of the keto diet. Normal mounts of shallots you’d find in recipes are so small that the carbs are almost insignificant.

Is Onion Powder or Dried Onion Good For Keto?

Some people might assume that dried onion flakes and onion powders are more low carb and keto-friendly than normal fresh onions. However, this is inaccurate, because dried onion and onion powder have just as many carbs and sugars as normal onions. You might even acquire more than one tablespoon of dried onion or onion powder to get the complete flavour of the onion.

How to use Onions and Remain in Ketosis?

While onions might not be the perfect low carb food for keto dieters, you can actually use them to remain in ketosis if you were to include them in your diet in small quantities. There are a few things you might want to consider before you jump for this opportunity.

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. Use them to add a little flavour to your food, as opposed to sugar, or sugary condiments, like BBQ sauce, ketchup and dressings that add impeccable flavours at the expense of carbs.

Onions contain carbs and sugars but are relatively low in both, so they can bring forth lots of pleasant flavour, helping you avoid the urge to use other flavourful ingredients, that could be worse for keto.

Try to use spring onions sparingly in your keto diet. The great thing about onions, is that scattering a pinch goes a long way. You probably won’t even need a whole cup of onion in your meal to get potent flavours, so cutting that amount down to a quarter cup will deliver some relatively low carb flavours that won’t pull you out of ketosis.

Keto Alternatives for Onions?

Onions might not always work for keto dieters, luckily there are some flavourful alternatives that can make your keto dishes more exciting and bold, without adding too many net carbs.

  • Garlic
  • Shallots
  • Green Onions


Garlic is one of the best low carb alternatives to onions for a keto diet. It is packed with potent flavours, and while it tastes much different from onion, it happen to carry the same bold taste that we all crave from our meals. Garlic is a low calorie and low carb vegetable that can be used to add an immense amount of flavour to culinary dishes. It’s also incredibly good for you, with promises of anti-inflammatory benefits.

Garlic can be used in many ways in low carb recipes. Although 100 grams serving of garlic does contain 33 grams of carbs, it’s important to remember that garlic is normally used to add a little flavour to dishes, rather than adding an entire chunk to a dish. Consequently you’ll only be using a handful of minced garlic cloves at a time.


Shallots are also a type of onion that produces potent flavours when added to meals. They do contain some carbs, but most keto dieters use less shallot in a recipe than they would a raw onion. Shallots have a strong taste, so you might choose to use a smaller portion of shallot that contains fewer net carbs overall.

A 100 grams serving of shallots contains around 17 grams of total carbs, including 3 grams of dietary fibre and 8 grams of sugar. This serving is about the same as white onions, but the total carbs added to your dish will most likely be lower when you’re cooking your keto meal.

Green Onions

Green onions or scallions also belong to the allium family, so they provide the same type of oniony flavour in recipes that beckon them. Like shallots, most people use smaller portions of green onions per keto meal, as there is much depth to their taste, compared to an onion. For a 1 cup serving, you can expect green onions to provide around 7 grams of carbs, 2.5 grams of dietary fibre, and just 2 grams of sugar. Most dishes will need a much smaller serving of green onions, so the carb content of what you’ll actually consume will most likely be minimal.

Eating Onions on Keto?

It’s perfectly fine to eat onions on keto, as long as you do not exceed your daily carb limit. Bear in mind that each type of onion carries more or fewer calories than its relatives. Consuming onions in large amounts is quite out of the ordinary, and whilst it’s not out of the realms of possibilities, you might choose to use onions in your meals or salads, therefore 1/2 cup of red, green, or white onion should be fine for you to enjoy without the fear of coming out of ketosis.


Is Tomato and Onion Allowed in Keto Diet?

Tomatoes contain much fewer carbs than other fruits, and are considered keto-friendly, and luckily onions can also fit into a keto diet when consumed in smaller quantities.

Do Cooked Onions Have More Carbs Than Raw?

If you’re comparing the carbs from a raw onion to a cooked onion then yes there are more carbs in cooked onion, because the water has been evaporated and you’re left with concentrated flavour.

Can You Eat Onions and Garlic on Keto?

Eating onions and garlic whilst on keto is perfectly fine as long as you eat them in moderation. You don’t need to add a chunk of garlic to your keto friendly meals, so a couple of minced garlic cloves should do the trick. Similarly with onions, you might choose to use less than a cup of onions for your meals, to stay within your daily carb limits.