What is Ketosis?

What is Ketosis?

Ketosis is a normal metabolic process characterized by increased ketone production. Ketosis happens when the body does not have enough glucose to make energy, so it burns fats instead. This results in a buildup of ketones in the blood.

Normally, your blood ketone levels are below 0.3 mmol/l. But after a prolonged fast or when you follow a ketogenic diet, blood ketone levels can rise to 3-7 mmol/l. When this happens, you are in ketosis.

About Ketosis

Your body can make energy from three macronutrients: carbohydrates, proteins, and fats. While the body can use any macronutrient to make energy, it is immediately and automatically drawn to using carbohydrates. This is because carbohydrates are economical, requiring fewer steps and less energy to fuel your cells. Another reason is that brain cells cannot use fats or proteins to make energy.

Before your body can utilize carbs, it needs to break them down into simple sugar molecules called glucose. Glucose then circulates in your blood so that your brain is never short of its main fuel supply. But what if you stop eating carbohydrates?

Well, in the absence of carbs, the body releases fatty acids to make energy. Because the brain cannot use fats, the liver converts a portion of the released fatty acids into ketones, which can now fuel the brain as well as the muscles and heart.

If you want to learn how to achieve this metabolic state, read our guide on how to get into ketosis.

Facts and Myths about Ketosis

Ketosis is a normal metabolic process but it is often portrayed in a negative light. Ketosis myths are mostly the result of it being confused with ketoacidosis, which is much more extreme. Researchers also disagree about the nature of ketosis, further feeding into these myths. Ketosis that is induced by diet is often referred to as Nutritional Ketosis.  Below, you will find common ketosis facts and myths explained.


Ketosis is normal.

Evolution designed ketosis to help us survive in times of starvation and food scarcity.  Further, the body is always in a mild state of ketosis. For example, following an overnight fast or a vigorous exercise, your blood ketone levels do increase [1].

Ketosis is healthy.

Ketosis provides a range of unique health benefits like glycemic control, weight loss, enhanced physical energy and endurance, mental clarity, and even cancer prevention. Ketosis also enhances autophagy, which is your body's recycling system linked to good health and longevity [2].

Ketosis takes time.

Despite what you may have been told, it takes time to get into ketosis. Before your body can start making ketones, it needs to deplete its 600g of glycogen stores [3]. Learn how long it takes for the body to go into ketosis.

Ketosis induction is difficult.

Before your body can make the switch to full-blown ketosis, it can go through a mild crisis period. This event is often called the "keto flu" and can last between 2 and 7 days. Symptoms of the keto flu include fatigue, pain, and nausea. The keto flu is fairly common. It tapers off as you get into ketosis.



Ketosis is dangerous.

Ketosis is not dangerous. It is a normal physiological reaction to low blood glucose levels and is an adaptive response. The reason ketosis is considered dangerous is that it is confused with ketoacidosis. Ketoacidosis is when blood ketone levels rise above a normal threshold to an extreme degree due to uncontrolled production. This only happens with untreated and uncontrolled Type 1 Diabetes, severe alcoholism, or starvation.

Ketosis is bad for diabetics.

People with Type 2 Diabetes can benefit from a ketogenic diet and being in ketosis. A growing number of studies is looking into ketosis as a treatment for Diabetes, often referred to medically as “Diabetes Mellitus” [4]. For people with Type 1 Diabetes, ketosis can also help manage their condition. However, Type 1 diabetics need to monitor their ketone levels carefully and to often adjust insulin medication to avoid ketoacidosis.

Ketosis makes you lose weight.

This one is true to some extent. Your body spends a lot of energy supporting ketosis, which can create an energy deficit. But if you eat a lot of fat, then you may be creating an energy surplus that prevents your body from burning its own fat stores. For this reason, many keto dieters and experts will tell you that keto-adaptation plays a bigger role in weight loss than ketosis.

Ketosis starves the brain.

This myth was created as a result of the assumption that your brain cannot survive without carbohydrates and glucose. This is simply not true. In fact, the brain can function normally on ketones, and even better than on glucose, in fact, according to current studies [5].


Ketosis is a normal process where your body produces ketones. It results from fasting or following a low-carbohydrate, high-fat ketogenic diet. The keto diet is surrounded by various facts and myths, and being able to differentiate between them helps you to reap the full benefits of keto.


  • While the body is immediately drawn to using carbohydrates for energy, it can also tap into an alternative fuel source in the absence of carbs -- ketones.
  • Ketones effectively fuel your brain, muscles, and heart.
  • Ketosis is healthy, takes time, and causes you to experience flu-like symptoms during the transition phase.
  • Ketosis is often confused with ketoacidosis, a complication of uncontrolled Type 1 Diabetes, severe alcoholism, or starvation.
  • Don’t take for granted the concept of energy balance even on a keto diet if you’re looking for weight loss.
  • Studies show that the brain functions better on ketones.


  1. Dhillon KK, Gupta S. Biochemistry, Ketogenesis. 2018 October 27 -
  2. Takagi A et al. Emerging role of mammalian autophagy in ketogenesis to overcome starvation. 2016 -
  3. Jensen J et al. The Role of Skeletal Muscle Glycogen Breakdown for Regulation of Insulin Sensitivity by Exercise. 2011 December 30 -
  4. Westerberg DP. Diabetic ketoacidosis: evaluation and treatment. 2013 March 1 -
  5. Murray AJ et al. Novel ketone diet enhances physical and cognitive performance. 2016 August 15 -

Join Over 200,000 Fans

Sign up for the Kiss My Keto mailing list to get free keto resources, recipes, and strategies from the largest keto brand in the world.