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What are Ketones? Types, Benefits, and How to Test


Research is ever-evolving into the best type of fuel for optimal health and performance. One such area of research is on the benefits of having your body running on ketones, or “ketone bodies,” rather than glucose.

But what are ketones exactly? They are an alternative fuel source used by the body when glucose stores are in short supply. This is what occurs on a low-carb, high-fat diet like the ketogenic diet, and is one of the primary reasons for its numerous health benefits.

Several studies show promising evidence that using ketones for energy can improve several health markers including:

  • Decreased inflammation (*)
  • Improved mental clarity (*)
  • Faster weight loss and increased satiety (* , *).

The ketogenic diet focuses on priming your body to function in a state of ketosis, where your body is primarily burning ketones from fats rather than glucose from carbohydrates.

Since we are realizing just how beneficial using ketones for energy can be, it’s important to educate yourself as to what ketones are.

This article explains ketones — from how they’re created to their benefits and low carbohydrate diets.

What Are Ketones?

Ketones, also known as “ketone bodies,” are energy molecules created by the liver from the breakdown of fats. Your body makes ketones when you don’t have access to carbs or enough glucose stores (glycogen), such as when on a ketogenic diet.

Although most people run on carbohydrates (glucose), studies show that burning fats (ketones) for energy is the healthier alternative (*).

Your liver produces three types of ketones:

Of the three ketone bodies, BHB is the one your body can use most effectively for energy.

That’s why most exogenous ketone supplements are made out of BHB salts.

The Difference Between Exogenous and Endogenous Ketones
Exogenous ketones are ketone bodies (mainly BHB) that are consumed in supplement form to boost your blood ketone levels. Meanwhile, endogenous ketones are made by the body, such as in the case of a ketogenic diet.

Exogenous ketones are a great tool for getting into ketosis faster and priming your body to use fat for energy (*).

How Are Ketones Formed in Your Body?

During the hunter-gatherer era, our ancestors relied on ketones as their main source of energy (*).

Fortunately, today, we can mimic these metabolic conditions to make ketones.

The Science Behind Ketone Production

The process of turning stored body fat into ketones is called ketogenesis.
Here’s how your body makes ketones:

When your body doesn’t have enough glucose for fuel — such as during a very low carbohydrate diet, fasting, or exercise — your body burns through its fat stores (*).

Fatty acids are released and transported to the liver where they’re converted into ketones (*). The main ketone bodies are acetoacetate (AcAc) and beta-hydroxybutyrate (BHB), while the third and least abundant is acetone (Ace) (*).

When you become efficient at making the right amount of ketones to burn fat and using those ketones for energy, this means you’re fat-adapted.

what are ketones

Are Ketones Bad?

Having ketones present is usually a good thing. In fact, your body constantly makes a small amount of ketones. Ketones are always present, and they normally increase when there’s a shortage of glucose (*).

However, there are instances where ketone levels may go above what is considered a safe level. This may happen in those with diabetes in a condition called diabetic ketoacidosis (which is more common in people with type 1 diabetes than type 2 diabetes) (*).

Nutritional Ketosis vs. Ketoacidosis

Nutritional ketosis happens when your body creates ketones for energy as a result of following a low carbohydrate keto diet. Then, you experience health benefits of this metabolic state such as increased energy, better focus, and lower inflammation.

Ketoacidosis is not the same thing as ketosis. Ketoacidosis, also referred to as diabetic ketoacidosis (DKA), happens when the blood ketone levels of people with diabetes rise to unsafe levels (usually above 3 mmol/L) and insulin levels decrease dramatically. This usually happens when diabetics stop monitoring their ketone levels, miss their insulin therapy consistently, and undergo stress (trauma, surgery, or an illness). DKA is potentially lethal because it turns the blood too acidic, which affects organ function.

It’s important to note that if you’re not diabetic, your risk of reaching DKA is extremely low.

Either way, it’s important to measure your ketones regularly the keto diet to ensure that your ketones are within the normal range of 0.5 – 3.0 mmol/L (*).

Measuring Ketones

It’s important to test your ketone levels when following a keto diet, to make sure your body is producing and using ketones for energy.

There are three main tests to confirm nutritional ketosis:

#1: Urine Testing

Testing your ketones in the urine is the cheapest (and a highly convenient) way to test your ketones, but the least accurate. You can buy ketone test strips at most pharmacies, and it’s an easy method for someone who’s just starting out on the ketogenic diet.

#2: Blood Testing

A blood meter is the most accurate way to test your ketones. However, it’s invasive (it involves pricking your finger) and it can be expensive if you test frequently.

However, if you value accuracy and can afford it, this method beats the rest.

#3: Breath Testing

Ketone breath meters are a non-invasive way to test your ketones through the acetone levels in your breath.

They are not as accurate as blood tests are, as drinking alcohol and the amount of water you drink can skew results.

When Should You Test Your Ketone Levels?

Once you start keto, it’s best to start checking your ketone levels daily to know whether you’ve reached the desired ketone level of of 0.5 – 3.0 mmol/L (*).

After that, it’s recommended to continue checking weekly.

It’s best to test your levels 3 hours after your last meal for the highest accuracy, and to ensure you’re in more of a fasting state (*).

Here are the signs and symptoms that your ketone levels may be too high, such as in the case with DKA (*):

  • A dry mouth
  • High blood glucose levels (greater than 240 mg/dL)
  • Intense thirst
  • Frequent urination

If left untreated, more severe symptoms may develop such as:

  • Fatigue
  • Confusion
  • A fruity breath odor
  • Nausea
  • Vomiting
  • Stomach pain
  • Trouble breathing

These symptoms are rare for the average person on the ketogenic diet, and are typically found in those with uncontrolled diabetes. If you experience any of these symptoms, speak to your doctor to have your ketone levels checked.

Ketones and Low Carb Diets

A high-fat, low-carb diet is what most effectively primes the body to produce ketones at a level to achieve health benefits. This is what the keto diet aims to do.

To reach optimal ketone levels, you must restrict your carb intake to less than 50 grams, and sometimes as low as 25 grams per day (*).

Once you start using ketones, you’ll notice you no longer feel hungry every two or three hours like you usually would on a carbohydrate-heavy diet (*). This is a big reason why many are so successful at losing weight on keto (*).


The research is clear on the benefits of using ketones as your primary energy source.

Although most studies on the benefits of ketones are new, using ketones for energy has been practiced for a very long time now.

If you’re currently on a high-carbohydrate diet and you’re not feeling your best, you might see positive changes by switching to a keto diet.

Ketones transform how your metabolism works so you can optimize your health and well-being, as well as prevent chronic diseases.

Frequently Asked Questions

What is a ketone?

Ketones or “ketone bodies” are energy molecules created from the breakdown of stored body fat. Your liver makes ketones when you don’t have access to carbs or enough glucose stores (glycogen), such as when on a ketogenic diet.

What do ketones do?

Ketones serve as an alternative fuel source used by the body when glucose stores are in short supply. They provide energy for the body and mind and provide several health benefits.

How do I test for ketones?

There are 3 main methods to measuring ketones — measuring ketones in urine, blood, and ketone breath tests. Blood ketone tests are the most accurate, but most expensive (and an invasive) way to test.

What’s the difference between nutritional ketosis and ketoacidosis?

Nutritional ketosis is what happens when your body creates ketones from reducing carbs in your diet. It’s completely different from ketoacidosis in which blood ketone levels rise to dangerous levels, and is common in those with poorly managed diabetes.

19 References

Bueno N et al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: A meta-analysis of Randomised controlled trials. 2013 May

Kosinski C et al. Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies. 2017 May 19

Paoli A et al. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. 2013 June 26

Bazzano L et al. Effects of Low-Carbohydrate and Low-Fat Diets. 2014 September 2


Stubbs B et al. On the Metabolism of Exogenous Ketones in Humans. 2017 October 30

Poff A et al. Ketone Supplementation: Meeting the Needs of the Brain in an Energy Crisis. 2021 December 23

Dhillon K et al. Biochemistry, Ketogenesis. 2022 February 10

Dhillon K et al. Biochemistry, Ketogenesis. 2022 February 10

Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. 1999 November to December

Dhillon K et al. Biochemistry, Ketogenesis. 2022 February 10

Lizzo J et al. Adult Diabetic Ketoacidosis. 2022 May 2

Gershuni V et al. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. 2018 September

Gershuni V et al. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. 2018 September

Urbain P et al. Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis?. 2016 November 4

Centers for Disease Control and Prevention. Diabetic Ketoacidosis.

Gershuni V et al. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. 2018 September

Alberti K.G et al. Hormonal regulation of ketone-body metabolism in man. 1978

Drabińska N et al. Recent advances in the application of a ketogenic diet for obesity management. 2021 April


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