What Are Ketones, and Why Are They Important?

Medically Reviewed By Megan Soliman, MD
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Ketones are chemical substances that develop as the body breaks down fat. A certain level of ketones in the body can be normal. However, having high levels of ketones may cause ketoacidosis, which is a serious complication that can have further effects on health. If the body does not have enough glucose, which is its primary source of energy, it breaks down fat as a substitute. This produces ketones.

This article explains what ketones are, what they mean for your overall health, symptoms and diagnosis of high ketone levels, and more. 

What are ketones? 

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Ketones and ketoacids are acid byproducts of the liver breaking down fatty acids. They function as an alternative energy or fuel source for the body when there is not enough glucose.

When the body begins to break fatty acids down into ketones, it enters a metabolic state known as ketosis.

Ketones are essential elements of a healthy body, but high levels of ketones in the urine or blood can be dangerous. Hormones such as insulin and glucagon allow the body to obtain a normal flow of glucose, preventing unhealthy blood ketone levels and a rise in blood sugar levels. 

However, conditions such as diabetes and certain other factors may lead to a buildup of ketones in the blood. Additionally, people following a low carbohydrate diet may have an increase in ketone levels because the body is more continuously burning fat. 

What do high levels of ketones do to the body? 

High ketone levels can be toxic. This is because the body cannot tolerate large amounts of ketones, which will eventually build up in the blood, altering its natural chemical balance. 

When blood and urine levels of ketones become too high, this can cause a condition called ketoacidosis.

Ketoacidosis has three principal forms:

  • Diabetic ketoacidosis (DKA): DKA frequently occurs due to an insulin deficiency, which can occur in people with diabetes — particularly those with type 1 diabetes. It may result from untreated diabetes or sudden physiological stress. In some cases, DKA can be a fatal complication of diabetes.
  • Alcoholic ketoacidosis: In people who have alcohol use disorder and those who drink alcohol at chronically excessive levels, ketoacidosis can occur. This is because when the body processes alcohol, it produces a byproduct called acetic acid, which is a type of ketone. This can cause ketones to build up in the body.
  • Starvation ketoacidosis: Prolonged periods of time with insufficient levels of food or nutrients can cause hypoglycemia, which decreases the production and secretion of insulin. This will cause the body to break down fats, producing ketones. Although it can be easily treatable, many clinicians miss the condition and do not make a diagnosis.

Learn more about DKA here.

Why are high levels of ketones dangerous? 

Ketones can be present in the urine and blood, altering the chemical balance in your body. In extreme cases, they can build up and be toxic to your system. 

This is because high levels of ketones can cause ketoacidosis, which can lower the blood pH and make the blood and bodily tissues too acidic. Clinicians may refer to this condition as acidosis.

Acidosis and ketoacidosis can further cause negative effects on health, such as coma, cardiac arrest, and death.

As a result, acidosis is an emergency medical situation and will require emergency medical care.

Ketones and ketogenic diets 

Following a low carb diet — including the ketogenic, or keto, diet — will lead to nutritional ketosis. With a lack of carbs for energy, the body will enter a state of ketosis wherein the body burns fat and produces a small amount of ketones to use as energy.

Although both ketosis and ketoacidosis involve the production of ketones, contrary to nutritional ketosis, ketoacidosis is a serious complication wherein the body is naturally producing high and potentially dangerous levels of ketones.

In fact, clinicians believe that nutritional ketosis may be relatively safe, as the ketones it produces remain in smaller quantities and do not alter the blood pH.

This is different from ketoacidosis, which causes the body to produce ketones in much larger quantities. These are then able to alter the pH of the blood and may be life threatening.

Always consult your doctor before making any considerable changes to your diet. As with all diets that exclude large food groups and types of nutrients, there may be side effects and health risks.

Signs and symptoms of high ketone levels

Symptoms of unsafe levels of ketones in the urine or blood may include: 

Severe symptoms requiring emergency care

If a person has developed DKA, they may develop severe symptoms.

Seek emergency treatment or call 911 for anyone experiencing the following signs or symptoms:

  • mental confusion
  • difficulty breathing
  • dry or flushed skin
  • a fruity smell to the breath
  • vomiting
  • high blood sugar levels

Learn more about monitoring your blood sugar levels here.

Testing and diagnosis

Testing for harmful levels of ketones in the blood can help a person receive the right treatment before symptoms become life threatening.  

To confirm ketosis or ketoacidosis, doctors will use a blood or urine test. You can also find ketone test kits available at pharmacies without a prescription. Your doctor or pharmacist will be able to guide you on which option may be best for you.

Different factors — such as diet, preexisting medical conditions, age, and medications — can affect the test results. As a result, those taking the test at home or in a medical facility may have to avoid eating or drinking for a few hours before taking the test.

When testing ketone levels at home, always follow the instructions on the kit and contact your doctor’s office for questions. Your doctor can advise you on the steps to take to carry out the test accurately.

Blood tests will collect a small amount of blood to measure the level of ketones in it. A home test may involve pricking the finger for a drop of blood.

It is recommendable that people with diabetes test for ketones when: 

  • Symptoms of DKA are constant.
  • Their blood sugar level is 240 milligrams per deciliter (mg/dl) or higher.
  • Their blood sugar level is normal, but they have unusual symptoms.

Research suggests that the ideal time to test for ketones is first thing in the morning or at least a couple of hours after eating food. 

If your test is positive or indicates high levels of ketones, contact your doctor immediately to discuss the diagnosis of the underlying cause. This will allow for effective treatment.


If a urine test is negative, it means that ketone levels are within a safe range or as expected.

Some tests may only produce the results as negative (free from high levels of ketones) or positive (indicating higher levels of ketones).

Other tests may indicate a range or amount, which can include

  • small or trace levels (15 mg/dl or under)
  • moderate levels (up to 40 mg/dl)
  • high levels (higher than 80 mg/dl)

A blood test may be more precise and present results that fall within the following categories: 

  • low (less than 0.6 millimoles per liter [mmol/l])
  • moderate (0.6 to 1.5 mmol/l)
  • high (1.6 mmol/l or above)

When to seek medical help 

Contact your doctor regarding any new or debilitating symptoms.

Seek emergency treatment for any severe symptoms.

Additionally, if you have a result that indicates positive or high levels of ketones, contact your doctor as soon as possible. Any result higher than 3 mmol/l requires immediate help, so you should call 911 or seek emergency care.


Treatment for high ketone levels can vary depending on the underlying cause.

Treatment for ketoacidosis may include:  

  • insulin therapy
  • electrolyte replacement
  • medications for underlying conditions
  • replacement of fluids and correction of acid in the blood 

Treatments may require admission to the hospital with frequent monitoring.


The key to managing high levels of ketones is to prevent buildups.

Maintaining a healthy lifestyle, including eating a well-balanced diet and getting regular exercise, is beneficial for your overall health. 

People with a history of diabetes can also take the following measures: 

  • monitoring their glucose levels daily
  • following their treatment plan
  • sticking to a nutritional plan that includes carbs 
  • staying hydrated
  • monitoring their ketone levels and keeping tests at home 


Ketone production is a normal response from the body to a shortage of glucose. It does not necessarily cause harm.

However, having high levels of ketones can be dangerous and present an emergency situation. In some cases, high levels of ketones causing ketoacidosis can be fatal.

Additionally, a 2016 study into the mortality rates of those who experience acidosis suggests that the likelihood of death may depend on the cause of the acidosis. The researchers also note that over half of the people who did not experience cardiac arrest survived.

However, they still emphasize the need for intensive therapy for everyone who experiences acidosis, including those who have non-extreme cases.

Those who experience DKA may have a risk of fatality due to infections or their treatment not working successfully.

Treatment can be effective and reduce further adverse health effects if accessed quickly, but a risk of fatality may remain in the long term.

In general, monitoring your symptoms and ketone levels is key to obtaining the right treatment. 


Ketones appear as a response to the body breaking fatty acids down to use for energy. As the body enters a state of ketosis, it will increase its ketone levels in the urine and blood. 

Although low levels of ketones in the body are expected and can be healthy, having high levels can be very harmful. This is because high levels of ketones can cause ketoacidosis, wherein the blood becomes acidic and toxic.

People with a history of diabetes should monitor their ketone levels to avoid developing DKA. This is a serious medical condition that commonly affects people with type 1 diabetes and certain individuals with type 2 diabetes

Treatment can include insulin therapy as well as electrolyte and fluid replacement.

Eating a well-balanced diet that includes carbs, getting regular exercise, and continuously monitoring blood sugar levels (for people with diabetes) is essential to prevent ketone buildup.

Seek emergency treatment for at-home test results that indicate high levels of ketones and for symptoms such as confusion, a fruity smell to the breath, vomiting, or difficulty breathing.

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Medical Reviewer: Megan Soliman, MD
Last Review Date: 2022 May 26
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