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How Long Does It Take to Get into Ketosis?

author avatar Dr. Eric Berg 02/13/2024

If you recently started the ketogenic diet, you may wonder how long it takes to get into ketosis. 

Restricting carb intake shifts your metabolism into a fat-burning mode which triggers profound changes in how your cells generate energy. While you can reach ketosis within a few days, it can take your body up to a month to fully adapt to using ketones as a primary fuel source.  

Let's look at how long it takes to get into ketosis and what steps you can take to speed up your keto-adaptation.    

Fuel know dialed on ketonesHow long does it take to get into ketosis?

How long it takes to enter ketosis and fully adapt to using ketones as a primary fuel source depends on several factors, including your previous diet, metabolic flexibility, body weight, and whether you are doing Healthy Keto® or a dirty keto diet. 

“Most people achieve ketosis within a few days and are fully keto-adapted within a month,” says Dr. Berg. “However, in some cases, it can take up to six weeks to adjust to the profound metabolic changes of keto.” 

If you have consistently restricted your carb intake and start to experience mental clarity, stable moods, diminished hunger sensations, and no longer have carb cravings, you most likely have entered ketosis, and your body adapted to using ketones as an energy source.   

Watch the video below to learn how long it can take for your body to adapt to keto.

What is the ketogenic diet?

The ketogenic diet is a low-carb, moderate-protein, and high-fat diet that primes your metabolism to burn fat instead of carbs as a fuel source. 

Keto’s low-carb dietary pattern significantly limits the body’s ability to utilize blood glucose as a primary fuel source which triggers the breakdown of fat to generate energy. 

How do you get into ketosis?

As your body breaks down fat, the liver generates large quantities of ketone bodies, a by-product of fat metabolism and a very efficient energy source. As ketones build up in your circulation to fuel your body, you enter a metabolic state called ketosis.  

To achieve ketosis and maintain fat-burning, limit your carbohydrate intake to no more than 20 to 50 grams of net carbs daily. Consuming high-carb foods can quickly push you out of ketosis, and your metabolism will return to burning blood glucose for energy.    

The longer you stay in ketosis, the more efficient your metabolism will become at burning fat—this is also known as keto-adaptation or fat-adaptation.   

Ketone tests

The best ways to test your ketone levels

You can test ketone levels in several ways, including blood ketone testing, breath ketone testing, and urine ketone testing. 

Here are the best ways to test your ketone levels:

Blood Ketone Testing

Using a blood ketone meter is the most accurate measurement of blood ketone levels. However, you must purchase the device and test strips and be willing to prick your finger to collect a small blood sample. 

Breath Ketone Testing

A breath ketone meter measures the levels of acetone in your breath. Acetone is a type of ketone and indicates that your body is in ketosis. Acetone is also the reason for keto-breath, a common symptom during the early stages of keto-adaptation. 

Urine Ketone Testing

Urine ketone testing strips are the easiest and cheapest way to test ketone levels, but also the most unreliable. 

Urine ketone testing is influenced by factors such as hydration levels and the time of day. In addition, as your body adapts to keto, your cells will become more efficient using ketones as a fuel source. This lowers urinary ketone concentration, meaning you can be in ketosis without ketones in your urine

You may have heard that elevated levels of ketones can indicate ketoacidosis, a serious metabolic disorder that can be life-threatening. It’s important to understand that ketoacidosis doesn’t develop as a result of keto or intermittent fasting and typically only affects individuals with diabetes.  

However, if you are experiencing symptoms including thirst, confusion, frequent urination, nausea, weakness, and fruity-scented breath, it’s essential to consult with a healthcare provider to determine possible underlying causes and formulate an appropriate treatment plan.  

Intermittent fasting clock

Five ways to speed up keto-adaptation

During keto-adaptation, your metabolism becomes increasingly more efficient at burning fat, and the liver produces more ketones to fuel your body.

Research published in Nature Reviews Neuroscience confirms that converting fats into energy relies on different metabolic pathways and enzymes than burning sugars, and it can take your cells weeks or even months to fully adapt to these changes.   

However, there are several ways that can help your body adjust to ketosis and lower the risk of suffering side effects of doing keto, including brain fog, fatigue, muscle cramps, and keto headaches. 

Here are five steps that you can take to speed up keto-adaptation.  

1. Combine keto with intermittent fasting  

Intermittent fasting helps with keto-adaptation because it accelerates the transition into ketosis by depleting the body's glycogen stores

Glycogen is a stored form of glucose that can be used for energy. When glycogen levels are low, the liver begins to use fat as fuel instead of sugars, which explains why intermittent fasting can significantly shorten the time it takes to reach and adapt to ketosis. 

Combining keto with intermittent fasting is an excellent way to support your metabolic health and has been found beneficial in the treatment of obesity, metabolic syndrome, and diabetes. 

A group of experts studying the health effects of ketosis concluded that “The use of intermittent fasting and a ketogenic diet is an effective and sustainable alternative to a standard care approach in the treatment of type 2 diabetes.”

2. Stay hydrated and replenish electrolytes 

During the early stages of keto, you may notice a more frequent need to urinate. 

Ketosis can cause temporary fluid loss and depletes essential electrolytes like potassium and sodium. Replacing lost electrolytes is crucial to support your cellular adaptation to ketosis. 

Increase potassium-rich foods like vegetables and salad, and aim for seven to ten cups of veggies daily to get optimal nutrients. 

Alternatively, replenish potassium with a high-quality electrolyte supplement without added sugars or dextrose.  

Digestive system

3. Support fat digestion 

A sudden high fat intake can initially overwhelm your capacity to digest and absorb dietary fats, and supporting your digestive system can help speed up keto-adaptation. 

Taking purified bile salts is a convenient way to support the digestion of dietary fats and enhances the absorption of fat-soluble vitamins, which promote cellular function and help your cells adapt to ketones as a primary fuel source. 

4. Eat nutrient-dense, high-quality foods 

A healthy keto diet doesn’t just require low-carb and high-fat foods. To support your body while adapting to the metabolic changes of ketosis, it’s important to do a Healthy Keto® diet

Healthy Keto replenishes vitamins and minerals by including plenty of green leafy vegetables, seafood, pork, avocado, full-fat dairy, and nuts and seeds. 

5. Boost B vitamins 

Switching to a high-fat diet can deplete B vitamins essential for burning fat. Lack of adequate B vitamins can slow down ketosis and prolong keto-adaptation. 

Doing Healthy Keto and incorporating nutritional yeast to support balanced B vitamin levels helps your body adapt to keto fast.  

Keto foods

Health benefits of keto

The ketogenic diet has gained increasing popularity—and for a good reason. 

Not only does keto help to lose body fat fast, but people that consistently follow keto report higher energy levels, sharper focus, and overall improved well-being.

In addition, research published in Cureus confirms that the keto diet supports metabolic health and lowers the risk of diabetes, insulin resistance, and metabolic syndrome.      

Here are some examples of why the keto diet is an excellent choice for your health: 

  • Rapid weight loss and healthy weight maintenance long-term

  • More energy and improved cognitive function 

  • Ketosis diminishes carbohydrate cravings and supports blood sugar balance 

  • A stronger immune system that can fight inflammation and infections more effectively

Dr. Berg and Ketosis

Key takeaways

Going keto has profound health benefits but also requires significant metabolic changes. While most people enter ketosis within a few days, it can take considerably longer for your cells to fully adapt to using fat as a fuel source. 

You can help your body to transition into ketosis faster by combining Healthy Keto with intermittent fasting, supporting fat digestion, staying hydrated, and replenishing electrolytes. 


1. What is ketosis?

Ketosis is a metabolic state in which your body burns fat for fuel instead of carbohydrates.

A low-carb diet triggers the breakdown of fats in the liver, which generates ketones, a by-product of fat metabolism and a very efficient fuel source. When ketones enter your circulation and fuel your cells, you achieve a metabolic state called ketosis.   


2. What are the first signs of ketosis?

Increased energy, clear focus, stable moods, and diminished cravings and hunger sensations are typically the first signs indicating that your body has entered ketosis.  

3. How quickly will my body go into ketosis?

This depends on several factors, including your body weight, how metabolically flexible you are, and how disciplined you are in restricting carbs. However, most people can enter ketosis within three to four days and fully adapt to using ketones as a primary fuel source within a month. 

4. How can I speed up keto adaptation?

Combining Healthy Keto with intermittent fasting, supporting fat digestion with bile salts, and boosting B vitamins and electrolytes helps your body adjust to using ketones as an energy source and combats common keto flu symptoms, including headaches and fatigue. 

5. Is it possible to adapt to ketosis in 24 hours?

No, it isn’t possible to fully adapt to ketosis within 24 hours. Your cells have to adjust to using ketones as an energy source which requires increased production of metabolic enzymes that help to generate energy from ketones. It typically takes between two to four weeks for your body to fully adapt to burning fat as a primary fuel source. 


6. What does it feel like when you’re in ketosis?

Most people experience increased energy and focus, stable moods, and diminished carb cravings when entering ketosis.  

7. How do I know if I’m in ketosis?

While there are some physical signs of ketosis, including increased energy, reduced appetite, and mental clarity, you can test your urine, breath, or blood ketone levels to determine if you are in ketosis. 

8. Can intermittent fasting speed up ketosis?

Yes, combining keto with intermittent fasting helps your cells to adapt to using ketones as a fuel source faster. Fasting depletes glycogen during the early stages of keto-adaptation, which helps to push your metabolism into fat-burning mode and ketosis. 

9. What’s the best way to test for keto adaptation?

Testing your blood ketones is the most reliable way to confirm if you are in ketosis and helps to determine keto-adaptation. However, blood ketone meters can be expensive, and using urine test strips or a ketone breath meter are convenient and non-invasive alternatives to test for keto-adaptation.  

10. Is keto flu a sign of ketosis?

Yes, experiencing keto flu symptoms can indicate your metabolism is shifting from burning sugar to using fat for energy. Ketosis triggers changes in hormones, electrolyte levels, and vitamin requirements, which can cause temporary symptoms, including headache, fatigue, and muscle cramps. 

11. Why do some people take longer to get into ketosis?

People with a very high-carb diet before switching to keto or those that consume more than 20 to 50 grams of net carbs daily typically take longer to get into ketosis and become fully fat-adapted.

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