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What Are Ketones?

Louise | July 7
What are Ketones? #keto

Ketones, ketosis, ketogenic, keto. If you’re confused, then this is the right place to be. Because I’m going to explain all about ketosis in this article…

Ketones are naturally produced by your body to use as fuel. Think of them as super useful little blobs of energy.

When you’re on a ketogenic diet, you’ll be producing more ketones and using them to fuel various cells in your body.

So, the point of a keto diet is to boost your ketone levels. And that’s why this entire post is about ketones. We’ll cover what they are, exogenous vs. endogenous ketones, how to measure your levels, and how to boost your production of them. Want to listen to what the experts have to say? Join me for episode 026 with Dr. Alexis Shields.


You may have heard ketones mentioned before, but do you actually know what they are and how they work? If you have no clue, don’t worry because I will run you through the basics, starting off with ketone bodies.

Ketone bodies are a natural source of energy.

In essence, a ketone body is what people are referring to when they throw out the term ‘ketones.’ These handy little fellows are created when fat is used by your body for energy.

Need more information? Watch Dr. Berg’s video explaining what a ketone is:

Usually, your body will use carbohydrates or sugars for energy before fat. This presents a problem if you want to lose weight, as the stored fat in your body is last on your body’s list of available fuels.

In essence, a keto diet is all about forcing your body to use your fat as fuel. Your body makes ketones by breaking down fat when your carbohydrate intake is low. They are created as a by-product when fatty acids are broken down in your liver. The process is called ketogenesis.

Bottom Line:

When you eat a low carb diet, your body uses your stored fat and fat from your diet as fuel. Your liver then breaks down those fatty acids and ketones are formed, which your body can also use for energy.


The Benefits of Ketosis

Ketones play a major part in the ketogenic diet. As such, they also play a major part in some of the health benefits you enjoy while on the ketogenic diet.

Here are some benefits you gain when your body is in a state of ketosis:

  • More energy (1)
  • Reduced inflammation
  • Lowered risk of heart disease (2)
  • Reduced risk of metabolic syndrome (3)
  • Greater mental clarity
  • Fewer cravings
  • Lowered cholesterol levels (4)
  • Effective weight loss (5)

Our bodies likely evolved to use ketones as an alternative energy source to cope with long periods without sources of glucose or other carbohydrates. (6) This also prevents the body from breaking down too much of your muscles (the protein in them) to create glucose via the process of gluconeogenesis.

When glucose isn’t readily available, the body will access fat stores and produce ketones. These help to transport energy to various parts of the body (including the heart) and keep us mentally alert by supplying energy to our brain cells.

In fact, they supply 75% of the energy needed by your brain during periods of starvation. (7) The theory is that you’ll then be able stay alert enough to hunt and scavenge for more food.

How are Ketones formed?

Because a keto diet is all about increasing the number of ketones in your system, it is important to know how this process works. Without a solid grounding in the science, you will find it hard to achieve a state of ketosis, which is when your body is steadily producing these molecules.

As you go about your day, your body is burning ‘fuel’ to keep you going. As you would expect, the most accessible fuels get used first, such as sugars and carbohydrates.

By burning these fuels first, your body ignores any stores of fat you may have. Once any easy energy sources run out though, your body turns to those fat stores and starts to use them.

“The most common way that we experience ketosis is when we do not eat for 10 or 12 hours overnight; we will often be in mild ketosis in the morning until we eat something with carbohydrates (sugar) in it,” according to Dr. Mary T. Newport, M.D.

She adds, “Ketosis becomes much more pronounced over days to weeks in people who are fasting intentionally, starving, or on a high-fat low-carbohydrate diet. In this situation, we begin breaking down fat into fatty acids after the glucose that is stored in our body is used up, usually within 36 to 48 hours.”

Ketones are a byproduct of this fat burning. The fat is broken down by the liver for the body to use as fuel and the ketones are created in the process as a way of moving that fuel around.

This is why measuring your blood ketone levels is a good indicator of how much your body is relying on stored fat for energy.


Endogenous Ketones

Those ketones produced naturally by your body are called endogenous ketones.

There are three types of these ketone bodies:

  • Acetone – produced in small quantities and not used by the body, formed from spontaneous decarboxylation of acetoacetate.
  • Acetoacetate (AcAc) – the first ketone produced and is responsible for transportation of energy from the liver.
  • Beta-hydroxybutyrate (BHB) – formed from acetoacetate and performs a similar function.

Exogenous Ketones

Ketones which are created artificially for use as a nutritional supplement are called exogenous ketones (AKA ketone supplements).

There are generally 3 types:

  1. Ketone Salts – e.g. beta-hydroxybutyrate combined with a salt. These are cheaper but raise blood ketone levels less than ketone esters.
  2. Ketone Esters – these are combined with an OH (alcohol) group. They often taste bad, are hard to produce, but raise blood levels more than ketone salts.
  3. Ketone Oils – oils like MCT oil can be easily broken down into ketones.

The main benefits of exogenous ketones are:

  • A boost in energy, which is great for athletes.
  • Greater mental clarity.
  • Therapeutic benefits.
  • Reduced appetite which can help you with your weight loss goals.
  • Reduction of the ‘keto flu’ symptoms, which people starting keto experience.

Registered Sports Dietitian and Strength and Conditioning Coach Justin Robinson notes that there are some drawbacks to using these as a supplement. “The possible disadvantages of exogenous ketones are their palatability and tolerance. Supplemental ketone esters are very bitter and cause significant gastric upset in some subjects.”

If you’re interested in trying exogenous ketones for yourself, take a look at our own Keto Upgrade.

Bottom Line:

What exogenous ketones can’t do is give you weight loss while you keep eating a high-carb junk diet. If you plan to take these supplements, then use them wisely in conjunction with a really healthy, nutrient-dense Keto diet.

Ketone Supplements

Supplements are usually made from Beta-Hydroxybutyrate. You don’t need ketone supplements to enjoy the benefits of a keto diet, but they can help with boosting mental energy as well as reducing keto flu symptoms.

So, if you want to give ketone supplements a try, then the brand I use is Perfect Keto.

Ketone Drinks

Ketone drinks are supplements that claim to help boost your ketone levels. These are just exogenous ketones in drink (or drink mix) format.

One of the most popular brands is KETO OS (also called Pruvit). (Pruvit) KETO OS is a drink mix (you add water to it). Its main ingredient is beta-hydroxybutyrate.

Another new brand is called HVMN Ketone. HVMN Ketone will be the world’s first ketone ester drink, and it’s designed for athletes.

Raspberry ketonesRaspberry ketones have made a big splash recently and there are a lot of supplements that contain them, but they actually have nothing to do with ketosis.

They are the chemical compounds that give raspberries their smell. These are completely different from the ketones produced by your body during ketosis. And the claims that they will help with weight-loss are unsubstantiated.

How to Measure Ketones

If you are keen on starting a keto diet, you will need to learn how to measure your ketone levels.

It can be really helpful to test levels to troubleshoot and optimize your diet by testing if you’re in ketosis or not.

In general, there are three ways of measuring ketones. Each method measures a different type of ketone with a different testing device.Ketones

1. Measuring Ketones in Blood

Ketones are transported to your cells via your bloodstream, so testing your blood is one way to test your ketone levels.

Which ketone is measured:Of the three you will find in your body, it is Beta-hydroxybutyrate (BHB) that is found primarily in blood.

What you’ll need to measure blood ketone levels:A blood ketone meter.Testing strips.

How the test works:This is very similar to measuring your blood glucose levels. To take the test, all you do is prick your finger to create a small drop of blood, which you place on the strip. The digital meter will then analyze the drop of blood and give you the ketone level readout after around 10 seconds.

What the blood ketone measurement tells you:BHB levels are often measured in millimol per liter (mmol/L). As a general guide, if you’re in ketosis then you will see a readout of 0.5-3.0mmol/L in your blood.

Advantages:This method for testing ketone levels is quick and very accurate.

Disadvantages:It’s expensive. The meter costs $45+ and the testing strips cost $1 each. Also, most people dislike pricking their fingers all the time.

2. Measuring Ketones in Breath

Dr. Stephen Ponder, M.D. notes that one of the first signs you’re in ketosis is the smell of your breath. “Ketones can be detected by smell. The ketone called acetone (nail polish remover) is removed through the lungs. A person with ketones may have a sweet fruity odor to their breath.”

Because the acetone can be found in the breath, testing the breath is one way to measure your levels.

Which ketone is measured:In breath, you’re measuring acetone, which is mainly excreted through your respiratory system. And it’s this ketone that’s responsible for keto breath (a sweet or fruity or metallic smell on the breaths of people in ketosis).

What you’ll need to measure breath ketone levels:A reusable ketone breathalyzer, e.g., a Ketonix device.

How the test works:All you need to do is blow into the device, which makes it a great non-invasive alternative to blood testing.

What the breath measurement tells you:The ketonix meter will give you a read out in ‘parts per million’ (PPM). (8)

BLUE : 0 – 4 PPM : Low KetosisGREEN : 4 – 30 PPM : Nutritional Ketosis RangeYELLOW : 30 – 80 PPM : Deep KetosisRED : above 80 PPM : Very Deep Ketosis

This corresponds to ranges found in various studies. (9)

However, these acetone breath measurements do not correspond well to blood BHB measurements.

Advantages:There are a range of these devices on the market and many will connect to an app on your smartphone to store and analyze your results. The meters are $150+ but they’re reusable so if you plan to do a lot of measurements, then this is a cheaper option.

Disadvantages:The meter can be difficult to calibrate and use. It’s not clear how acetone in breath is related to blood levels. Measuring the blood level is still the most accurate indicator of ketosis.

3. Measuring Ketones in Urine

Excess ketones are excreted in your urine, so a popular way to measure them is to use urine test strips.

Which ketone is measured:Acetoacetate is measured in the urine.

What you’ll need to measure urine ketone levels:Cheap ketone urine tests strips – you can get a 120 pack for less than $20.

How the test works:Pee on a strip, shake off any excess, then wait for around a minute.

What the urine strips colors tell you:When you’re in ketosis the strip will change to a purple color. You can refer to the packet for what the varying shades of purple can mean for your ketone levels in urine. What this method won’t give you is an exact number of ketones in your system.

Advantages:It’s cheap and easy. They can be a cheap and effective way for type 1 diabetics to check whether or not they’re entering ketoacidosis.

Disadvantages:Very inaccurate readings. For example, if you drink a lot of water, you’ll dilute your urine and the strips will indicate a low measurement.Ketones

What are your optimal ketone levels?

The main focus of a ketogenic diet is to get your body into ketosis.

This is why testing for ketones is such a big deal and why everyone is striving to understand and achieve optimal levels.

However, there is no set level that every person should strive for. The level you aim for will depend on your goals and needs.

There are a lot of different professional opinions about optimal blood levels out there, but, in general, they fall into the following guidelines:

  • Weight Loss – anything above 0.5 mmol/L
  • Improved Athletic Performance – anything above 0.5 mmol/L
  • Mental clarity and greater ability focus – 1.5 – 3 mmol/L
  • Therapeutic purpose: (e.g. managing epilepsy symptoms) – 3 – 6 mmol/L

The above guidelines are for people who can regulate insulin normally in their bodies. People with blood sugar issues may experience much lower ketone levels.

There are also a lot of factors that come into play that can impact your results:

  • If your body is very good at processing and using ketones, your levels could be very low, even though you are well into ketosis.
  • Some people use energy much more efficiently than others. On the other hand, you may need more than the recommended levels to achieve the energy you need.

Bottom Line:

Your optimal levels depend on your specific goals with a keto diet (weight loss, mental clarity, etc).

Ketosis and Weight Loss

Having a high level of ketones in your system can help you along the path to weight loss, but they will not do all the work on their own.

Additional weight loss benefits of following a keto diet include:

  • Fewer cravings.
  • Lowered sense of hunger and a lower caloric intake.
  • More energy for physical activity.

All the above are a big help to anyone who wants to lose weight, but they do not eliminate the need for a healthy diet and exercise.

The biggest mistake you could make is relying on only high ketone levels to get the results you need!


How do you boost your ketone levels if you need to?

You can achieve ketosis by:

  • Reducing your intake of carbohydrates (glucose). When your body runs out of glucose as fuel, it’ll switch over to burning fat and generating ketones.
  • Including healthy fats and oils, such as coconut oil and MCT oil into your diet. These could help make getting into ketosis easier.
  • Increasing physical activity to deplete your glycogen stores faster when you first start keto. This will use up your body’s stores of glucose so that it can switch to burning fat faster.
  • Fasting, where you limit or stop your food intake for a short amount of time. People will often fast for between 8 hours and 3 days to kickstart ketosis. This also works by depleting your glucose stores very quickly.

The most important thing to remember when starting a keto diet is to monitor your results and adjust as necessary. What works for someone else may not be the right thing for you.

You can take supplements to boost your ketone levels, but you should use these with the understanding that they will not work on their own.

Registered Dietitian Kylene Bogden, RDN, LD notes that “Ketone supplementation may provide you with that ‘special feeling’ (a deep state of ketosis), but it is not providing your body with any form of nutrition or added metabolic health benefits.”

While supplements can help you stay in ketosis and promote fat burning, if you are not following a keto diet you will only be wasting your time and money.

The recommended way to boost ketone levels is through diet.

Bottom Line:

Although taking exogenous ketones is an “easy” way to raise your ketone levels, but it might not help you reach your health or weight goals.

Eating a healthy Keto diet and raising your body’s natural production of ketones will give you a lot more health benefits (especially weight loss).

Diabetes and Ketoacidosis

If you have type 1 diabetes or end-stage type 2 diabetes, then you need to know about ketoacidosis before trying a keto diet. This is a serious medical condition that can occur in type 1 diabetics (and in end-stage type 2 diabetics).

According to Registered Nurse Eva Elisabeth Oakes, RN, and Dr. Louise Cole, “[Diabetic ketoacidosis] (DKA), primarily a type I diabetes complication, occurs mainly in younger adults and people in their teenage years. DKA can develop in a new-onset type I diabetic or a diabetic who misses insulin doses.”

During ketoacidosis in diabetics, the body is in a state of ketosis even when there is a high level of blood sugar, and the body’s pH is lowered to dangerously acidic levels. This is all connected with the inability of a diabetic’s body to create insulin to regulate blood sugar.

The combination of high blood sugar and high ketone levels can have disastrous consequences. In the most serious cases, those with ketoacidosis can fall into a life-threatening coma.

You can learn more about ketoacidosis here, and if in any doubt about how the keto diet could affect you, please consult your doctor.

The information provided on this website is for educational purposes only – it’s not intended to diagnose, treat, or provide any specific medical/nutritional advice. And since we’re not doctors or nutritionists, we highly recommend you get advice from a qualified, licensed medical professional. 

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Louise co-founded Louise's Foods, Paleo Living Magazine, Nourishing Brands, & CoBionic. She has considerable research experience but enjoys creating products and articles that help move people just a little bit closer toward a healthy life they love.