This Dr. Axe content is medically reviewed or fact checked to ensure factually accurate information.
With strict editorial sourcing guidelines, we only link to academic research institutions, reputable media sites and, when research is available, medically peer-reviewed studies. Note that the numbers in parentheses (1, 2, etc.) are clickable links to these studies.
The information in our articles is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.
This article is based on scientific evidence, written by experts and fact checked by our trained editorial staff. Note that the numbers in parentheses (1, 2, etc.) are clickable links to medically peer-reviewed studies.
Our team includes licensed nutritionists and dietitians, certified health education specialists, as well as certified strength and conditioning specialists, personal trainers and corrective exercise specialists. Our team aims to be not only thorough with its research, but also objective and unbiased.
The information in our articles is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.
Exogenous Ketones: How They Help During Dieting or Exercising
November 14, 2018
Researchers believe that humans, and many other animal species, too, developed the capacity to produce ketones (or ketone bodies) in order to prolong survival during periods of caloric deprivation. (1) Ketones are beneficial for our muscles, brains and other tissues during times of stress — such as when we’re intentionally restricting calories because we’re fasting, cutting out carbohydrates from our diets or doing endurance exercise. (2)
What is a ketone supplement exactly, and what would be the purpose of using one? Ketones are considered the most energy-efficient source of fuel for the body, releasing high amounts of ATP (adenosine triphosphate), which is often referred to as “the energy currency of life.” Not only can your body make ketones in response to things like fasting or very low-carb, very high-fat dieting, but you can also acquire ketones from exogenous ketone supplements.
Exogenous ketones, such as ketone esters and BHB salts, help to amplify the many positive effects of the ketogenic diet — while also mitigating “keto flu” symptoms like fatigue and brain fog.
Other benefits associated with ketone supplements include:
- helping you to shed excess weight
- controlling hunger and cravings
- supplying your brain with an energy supply, which boosts cognitive performance
- helping you to perform physically and recover more easily from exercise
What Are Exogenous Ketones? What Do They Do?
Exogenous ketones are ketones supplements that come from outside the body. What do exogenous ketones do? Exogenous ketones mimic the effects of ketones that are naturally produced by our bodies under certain circumstances. The liver naturally produces endogenous (meaning inside) ketones while in the metabolic state of ketosis, while exogenous (meaning outside) ketones are those provided from supplements.
What are ketones exactly? Ketones are defined as intermediate products of the breakdown of fats in the body. When you follow a very-low carb, very-high fat diet — also known as the ketogenic diet — your body starts producing organic ketone compounds, which serve as an alternative fuel source to carbohydrates. Basically, the keto diet fires up your fat-burning capacity by changing the way your body utilizes energy.
Ketones (or ketone bodies) are made when:
- Someone is following the keto diet (also referred to as a very-low carb ketogenic diet, or VLCKD), which puts them in the metabolic state called ketosis. Most low-carb diets will not lead to increased ketone levels, only the ketogenic diet can effectively do this. To stay in ketosis you need to get 70–80 percent of your daily calories from fat, no more than 20–25 percent of calories from protein, and no more than 5–10 percent carbs of daily calories from carbohydrates.
- Someone is fasting for 16 hours (intermittent fasting) or more, or purposefully restricting their calorie intake.
- Or if someone is starving.
- Ketone production is also boosted by high-intensity/endurance exercise, especially if it lasts more than 60 minutes.
The human body produces three types of ketones: (3)
- Beta-hydroxybutyrate (BHB) — accounts for roughly 78 percent of total ketones in the blood.
- Acetoacetate (AcAc) — accounts for approximately 20 percent of ketones in the blood.
- Acetone — accounts for only about 2 percent of ketones in the blood.
Beta hydroxybutyrate (or BHB) is the most abundant type of ketone that we produce, helping to provide the bulk of energy when our diets are nearly devoid of all carbohydrates. While there’s three types of ketone bodies, the ketone found in exogenous ketone supplements is usually only or mostly beta-hydroxybutyrate (BHB).
Exogenous ketone are usually taken to boost the effects that the keto diet and intermittent fasting have to offer. Exogenous ketone bodies have functions and benefits that include:
- Helping you to get into ketosis more quickly
- Mitigating side effects associated with ketosis, such as irritability, headaches and fatigue
- Supporting weight loss, especially fat burning
- Improving metabolic pathways, including preventing or treating diabetes and insulin resistance
- Suppressing your appetite
- Fighting cancer
- Reducing anxiety
- Helping to protecting the brain and cognitive health, including decreasing the risk for neurodegenerative diseases
- And potentially increasing lifespan/longevity
Here’s more about how exogenous ketones can support both physical and cognitive health:
1. Helps You Transition Into Ketosis
You can use exogenous ketones to help you transition into ketosis (the metabolic state where your body is using fatty acids for its primary source of energy) more easily and quickly, since ketone supplements supply your body with a direct source of ketones that are easily used as fuel.
Once you’re in ketosis, you’ll experience benefits including: more stabilized blood sugar, reduced hunger/cravings and help with loss of excess body fat. If you take a break from the keto diet (let’s say you’re carb-cycling, for example), then you can use ketone supplements for support transitioning back the diet.
Taking a ketone supplement may also help you avoid keto flu, the cluster of symptoms that occurs when the brain has no glucose for energy and before the liver is producing generous amounts of ketone bodies. Keto flu can lead to diarrhea, cramping, nausea, constipation, bad breath, overall weakness and rash, but these symptoms abate after you’re in ketosis (or when you supplement with ketones). (4)
2. Can Help With Fat-Burning & Weight Loss
How do ketones help burn fat? As mentioned above, they’re beneficial for getting you into ketosis. However, taking ketone supplements may not lead to weight loss if you aren’t also following a very low-carb ketogenic diet.
In other words, ketone supplements are helpful for keeping you in ketosis, but they aren’t a magic bullet when it comes to weight loss. You will still need to track your fat, protein and carbohydrate intake (at least at first) to make sure you’re actually in ketosis and burning fat. Once you have a good idea of what it takes to stay in ketosis, you can use exogenous ketones to keep your energy up and to decrease symptoms that mess with your success, such as fatigue and cravings.
You may also use exogenous ketone supplements to deepen your level of ketosis while practicing intermittent fasting, as your body begins to product some ketone bodies after 12 hours of fasting.
3. Can Improve Energy Levels & Prevent Fatigue
Exogenous ketones can be used to help improve energy levels, power output, physical performance and recovery from exercise. (5)
In some animal studies, researchers use ketone esters to increase rats’ blood ketone levels and to test the effects on their physical performance, cardiovascular functioning, and more. In one study, when rats were given chow (food) that was supplemented with the ketone ester called (R)-3-hydroxybutyrate that accounted for 30 percent of their daily calories for five days, the rats could run 32 percent further on a treadmill compared to rats eating a diet supplemented with either equal amounts of corn starch or palm oil. (6)
4. Help to Decrease Brain Fog & Improve Mental Performance
When glucose is not available from your diet, fatty acids as well as ketone bodies can be metabolized by the brain. Studies have found that ketones benefit cognitive/mental health by: improving cognition in memory-impaired adults, focus, attention and learning, (7, 8)
In the same rat study mentioned above, ketone-fed rats were able to complete a maze test 38 percent faster than rats fed the control diet because they made significantly more correct decisions prior to making a mistake.
Ketones may also prevent the formation of free radicals in the brain that can damage mitochondria can contribute to neurological problems. (9)
5. Helps Improve Metabolic Functions
In certain animal studies, giving exogenous ketones to rats has been shown to decrease blood glucose and insulin levels, even when the rats are eating highly processed diets high in refined carbs like corn starch. (10) Ketone esters are also used to raise ketone levels while simultaneously lowering cholesterol and triglyceride levels.
6. May Fight Some Cancers
A newer branch of research on ketone supplements, there is some hefty research completed in animals that suggests exogenous ketones (both with or without adherence to the keto diet) may help slow or stop the growth of cancer. When animals with metastatic (late-stage, multi-organ) cancer are given ketone supplements, they seem to survive up to 69 percent longer than control subjects. (11)
This may be due to the effect of both the ketogenic diet and ketone supplements to independently influence the Warburg effect, a little-understood action that aids the growth of cancer cells. (12)
7. Could Reduce Anxiety
Research studies have found that exogenous ketone supplementation may reduce symptoms of anxiety, even when the animals were not following a ketogenic diet. (13)
8. Helps Regulate Blood Sugar
Again with or without a keto diet, ketone supplements help to decrease blood glucose levels, suggesting that they may be helpful for diabetics. (14)
9. Improves Exercise Performance and Recovery
Have you ever heard that ketosis makes it harder to perform physical tasks or work out? Nothing could be further from the truth! In fact, entering a state of ketosis has no noticeable impact on even high-intensity exercise performance. (15)
But the news gets better — exogenous ketones may actually increase both exercise performance and muscle recovery. (16) This could be particularly helpful for high-intensity athletes who wish to follow a ketogenic lifestyle.
Types: Ketone Salts & Ketone Esters
There are three main types of ketone supplements:
- Ketone salts (sometimes called BHB salts), which are ketones that are bound to minerals, including sodium, calcium, magnesium or potassium. (17) The minerals in ketone salts can actually help to decrease keto side effects, such as muscle weakness and digestive issues. Ketone salts are typically the type used in powdered ketone products, which contain some combination of BHB, sodium and other ingredients.
- Ketone esters, which are basically “raw ketones” that metabolize quickly into BHB. This type is not widely available for most consumers but is typically used in research/studies. While esters have the benefit of raising blood ketone levels quickly, they are also notorious for tasting terrible and causing unpleasant digestive issues. However, new ketone ester products are now hitting the market that claim to taste better and work rapidly. (18)
- Ketone oils, which can include MCT oil. MCT (medium chain triglyceride) oils are used to boost ketones and help with fat burning. They may also support training, exercise performance and growth of lean muscle mass. (19) Coconut oil also contains medium chained triglycerides, but MCT oil is a more concentrated source. MCTs must be broken down first before they can be used for energy, making this type of supplement slightly less effective than ketone salts or esters.
Beta-hydroxybutyrate is the most active type of ketone body that can be used by your tissues for energy, so that is the ketone that most exogenous ketone supplements aim to increase.
Ketones can be taken in various forms including: capsules, oils, powders or drinks. No matter which type you use, it should be able to help raise BHB levels by supplying you with an immediate usable source of ketones. Some products will provide medium-chain triglycerides (MCTs) to help with your natural production of ketones.
Products may also contain other ingredients that support ketosis and decrease keto flu symptoms, such as bone broth, caffeine, coffee or coffee extract, apple cider vinegar, spices, collagen, probiotics and/or adaptogen herbs like ashwagandha. Because powdered ketone supplements don’t tend to have the best taste, other ingredients like cocoa, vanilla extract or stevia may be used to enhance the flavor.
Different ketone products also vary in terms of their calorie and macronutrient content. Some contain only fat, while others provide an ideal ratio of both fat and protein with very minimal carbohydrates (this is typical of some powdered products that are used to make ketone drinks/smoothies/shakes). One advantage of using capsules and powdered ketone products is that they are easy to travel with, shelf-stable and can be mixed with other ingredients to make their taste more appealing.
Exogenous Ketones vs. MCT Oil
The very best foods for increasing natural ketone production are healthy fats — especially MCT oil, butter, and coconut oil.
- MCT oil is a very popular food/supplement among people following the keto diet because it can be used to quickly increase fat intake, boost natural ketone production, increase energy, support digestive health, and reduce appetite and cravings.
- MCT stands for “medium chain triglycerides,” which are a type of fat that your body is capable of breaking down into ketones easily and quickly. Coconut oil contains MCTs (as do some other foods like cheese, butter, whole milk and yogurt) but not as much as MCT oil. MCT oil is a more concentrated source of medium chained fats, making it ideal for supporting ketosis.
- MCT oil has an advantage over exogenous ketones when it comes to cost. It tends to be less expensive than many exogenous ketone supplements.
- What are ways that you can use MCT oil? MCT oil can be taken just like a supplement, by having a tablespoon on its once daily. You can also add a tablespoon or more to your keto coffee in the morning, a shake or smoothie. It’s mostly flavorless but does add fattiness/creaminess to anything it’s mixed with. It tends to be easy to digest and can be better tolerated than some ketone supplements.
- Many people choose to use emulsified MCT oil because it mixes well with beverages and does not have an oily residue. It tends to have a better flavor than certain keto supplements and is masked easily by other keto diet foods and ingredients.
- While the most common way to consume MCT oil is in liquid oil form, there are now also some newer dried MCT oil powders available. These can be used like other exogenous ketone powders, such as added to keto shakes, smoothies or coffee.
How to Get Exogenous Ketones in Your Diet
How & Why to Use Exogenous Ketones:
By now it should be clear that the benefits of adding a ketone supplement to your routine include: helping with the transition into a state of ketosis, supporting energy levels when in a fasted state, preventing keto flu symptoms, and improving athletic/exercise performance and recovery.
Ketone supplements can be used in between meals or before a workout to provide you with a quick source of ketones. You can also use ketone supplements to help you get back into ketosis more easily and quickly if you’ve abandoned the diet for a period of time.
They can be taken with food or on an empty stomach, but may be more impactful if you take them on an empty stomach (such as first thing in the morning) or when fasting. If you’re using a powdered ketone supplement, try mixing one scoop/serving with about 12 ounces of water, plain almond milk, coffee or tea. Ketone drinks/smoothies can be enjoyed warm or cold.
Exogenous Ketones Supplementation & Dosage:
- How you use exogenous supplements depends on your goals. Because there are many types of ketone products available that are used differently, always read directions and dosage recommendations.
- You might use exogenous ketones for about 3–5 days while you’re transitioning into ketosis. Use about 1/2 to 1 serving (such as one scoop or 3–6 capsules) per day. Another approach is to try having smaller amounts/doses spread throughout the day so your body has a steady supply of energy coming in. Depending on the type of product you use, it might be recommended that you take 1/3 – 1/2 of a scoop/serving at a time, several times per day.
- To help keep keto side effects to a minimum, you might decide to have one scoop of a ketone product in the morning, or to use half a servings 1–3 times per day.
- For help with exercise performance and recovery, use one serving/scoop about one hour before a workout.
- If you’re taking keto capsules, a typical dose will be about 6 capsules daily with 8 ounces of water. Capsules can be taken with or without food.
How to Balance Ketones on the Keto Diet
Remember, while ketone supplements may have a number of benefits, you can still naturally increase/optimize your own production of ketones, which may have more lasting health effects. Other than taking exogenous ketones, there are also dietary changes you can make and other lifestyle habits that increase ketone production. These include: eating a very-low carb, high-fat diet (aka the keto diet), fasting and doing intense exercise (especially if it lasts more than 90 minutes).
To really maximize ketone production and enhance effects like fat-burning, you can combine a ketogenic diet, intermittent fasting, exercise and exogenous ketones like ketone capsules, a powdered product or BHB salts.
If weight loss is your primarily goal, you’ll want to track your progress. What level of ketosis is good for weight loss?
- The optimal range of blood ketone levels is between 0.6-6.0 mmol/L, depending on your goals and the condition you’re treating. When you’re not purposefully limiting carb take, levels will stay below 0.5 mmol/L.
- Quality ketone products can help increase your blood ketone levels to as high as 1.5 mmol/L. Following a keto diet correctly can increase levels even more. Most people on the keto diet will have ketone levels between 2-3 mmol/L. (20)
- For general weight loss, aim to get your ketone levels above 0.6 mmol/L.
- Doctors may sometimes aim for higher levels of ketones in patients that are being treated for therapeutic purposes, up tp 3-6 mmol/L. (21) But with this level of ketosis, it’s best to be monitored and to work with a practitioner.
Wondering if the keto diet is safe, and what potential side effects exogenous ketones might have? Side effects associated with ketosis can include: unpleasant taste in your mouth, fatigue, weakness, indigestion, dizziness, low blood sugar, sleep related issues, mood changes, frequent urination, constipation, cramps, and trouble exercising or recovering.
With time your body gets used to being ketosis and producing more ketone bodies, so symptoms should only be temporary and last for about 1–2 weeks. Ketone supplements should not make symptoms worse, but can sometimes cause loose stools/diarrhea. If this happens, decrease your dosage until you notice improvements. Be sure to drink enough water, rest and sleep enough, and to not over-exercise while you’re dealing with any keto side effects.
- Exogenous ketones are ketones supplements that come from outside the body. Exogenous ketones mimic the effects of ketones that are naturally produced by our bodies under certain circumstances, including when following the keto diet or fasting.
- Benefits associated with ketone supplements include: help transitioning into ketosis, help staying in ketosis, decreased keto flu symptoms, more energy, enhanced physical performance and recovery, and improved cognitive health/mental performance.
- There are three main types of ketone supplements: ketone salts (sometimes called BHB salts), ketone esters and ketone oils (such as MCT oil). Ketone products some in various forms: liquid, oil, capsules, extracts or powdered mixes.
- You can use exogenous ketones for about 3–5 days while you’re transitioning into ketosis, have smaller amounts/doses spread throughout the day so your body has a steady supply of energy coming in, have a scoop of a ketone product in the morning to help keep side effects away, or use one serving/scoop about 30 minutes to an one hour before a workout. If you’re taking keto capsules, a typical dose will be about 6 capsules daily with 8 ounces of water
- Ketone supplements are usually well-tolerated, but some have an unpleasant taste. When used in high doses they may be cause diarrhea and GI issues, so start slowly and increase your dose depending on your reaction.