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June 16, 2022

9 Signs and Symptoms You’re In Ketosis

Signs and Symptoms You’re In Ketosis Without Testing

What are the signs and symptoms you’re in ketosis? Ketogenic is becoming more popular and has been shown to be an effective way to lose weight. In short, the keto diet is low-carb, and high-fat which raises ketone levels.  There is a reduction in insulin levels and an increased breakdown of fats on a keto diet. These changes lead to several biological adaptations by the body and are associated with certain physiologic changes that let you know that you are in ketosis – breaking down fats for fuel.

Per our previous article, there are several signs and symptoms you can gauge to determine if you have achieved ketosis while following a ketogenic diet. Ketosis is a metabolic state in which ketones become an important source of energy for the body and brain. Ketosis occurs when carb intake and insulin levels are low forcing the body to burn fats for fuel. Ketones are produced during the metabolism of fats.

Here are the main signs and symptoms you’re in ketosis:

  • bad breath which is caused by a ketone called acetone
  • weight loss
  • reduced appetite
  • headache
  • nausea and other digestive issues
  • brain fog
  • fatigue
  • increased focus and energy
  • a short-term decline in performance
  • sleep disturbance

Bad Breath

Bad breath is a common symptom in those following a ketogenic diet. The change in breath is usually described as a fruity smell and is caused by elevated ketone levels, especially acetone. Frequent brushing of teeth and use of chewing gum (sugar-free of course) can help. The alteration in your breath is a positive sign, though, that you are in ketosis. Urine can also have a fruity smell.

Weight Loss

Weight loss is a major reason people try a ketogenic diet. The ketogenic diet is a low-carb diet higher in healthy fats and proteins than the typical American diet. Insulin is a fattening hormone. Little insulin is produced if following a ketogenic diet. Low insulin levels allow the body to burn calories from fat stores. Weight loss on a ketogenic diet can occur quite rapidly. The initial weight loss during the first week on the diet is usually related to burning up stored carbs and water rather than actual fat but once they are in full ketosis subsequent weight loss comes from previously-stored fats.

Reduced Appetite

By consuming more fats and protein on ketogenic diet satiety (sense of fullness) is achieved more quickly preventing overeating. The increase in protein intake and focus on vegetables rather than starchy carbs likely alter hunger hormones, too.  In addition, the ketones produced in the diet may also affect the brain reducing appetite. A ketogenic diet prevents rapid spikes in insulin which occur with higher carb diets. Insulin spikes are followed by drops in insulin levels leading to wide swings in glucose levels. When glucose levels drop too much hunger is triggered. Because the keto diet does not produce rapid swings in blood glucose and insulin levels the triggering of hunger is minimized.


The headache associated with a ketogenic diet occurs in the first week and may last a week. It is a result of the switch in metabolism and change in hormone levels that occur when the body adapts from obtaining energy from carbohydrates to fats. You can think of it as going through carb withdrawal. This transition from carbs to fats is called the induction phase. Staying well-hydrated can minimize headaches.

Brain Fog

Brain fog can occur for the same reason headaches occur. Plus, the brain is used to using carbs for energy and now must adapt to using ketones and there can be an adjustment period to achieve that. Many individuals more or less ease into a ketogenic diet but these early side effects symptoms can be minimized by going as low-carb as possible from the get-go. Once the brain gets used to burning ketones, brain function will be optimized and the brain fog will be lifted.

Nausea and Digestive Issues

Anytime you make a change in diet you may experience gastrointestinal symptoms as your body adjusts to eating different foods. The gut contains billions of bacteria (gut microbiome) and the makeup of those bacteria will change with a change in diet. This can lead to diarrhea, constipation, nausea, and bloating. When this happens on a ketogenic diet the symptoms typically last 1-2 weeks. Be sure to eat low-carb vegetables for their fiber which will minimize constipation.


This can be mental fatigue (brain fog as discussed above) or physical fatigue. Water loss is common in the early stage of a ketogenic diet and with that can come to a loss of electrolytes. Replacing those lost electrolytes (potassium and magnesium) can offset some of the physical fatigue.

Short-term Decline in Physical Performance

A decline in physical performance occurs from the rapid reduction of glycogen stores (carbohydrates) stored in the muscles and liver. Glycogen is used as the primary fuel source during high-intensity exercise. The performance will return to normal in a few weeks on the ketogenic diet. Switching to a ketogenic diet may be beneficial for those competing in ultra-endurance events where the metabolism of fat becomes more pronounced.

Increased Focus and Energy

Increased focus and energy seem to contradict the fatigue and brain fog that some experience on a ketogenic diet. The increase in focus and energy is a late occurrence or long-term effect of a keto diet while the fatigue and brain discussed previously are easy or short-term effects of the diet. Ketones are a potent source of fuel for the brain and many long-term keto advocates report increased clarity and better brain function.

Sleep Disturbance (Bonus)

This is a short-term effect as the brain adjusts from burning carbs to burning ketones for fuel. It is thought that switching from a predominate carb diet to a keto diet alters the production of melatonin and serotonin which help regulate sleep. In the long-term many reports improved sleep on a keto diet. Staying hydrated, making sure your electrolytes are being replaced, getting regular exercise, and engaging in relaxation techniques can minimize the temporary sleep disturbance related to the initiation of a ketogenic diet.

So there you have 10 ways to know if you have achieved ketosis without even testing.  But, are there ways to test to absolutely know for sure if you have achieved ketosis. The answer is “yes” and the topic of a future article.

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Dr. Joe Jacko

Dr. Joe is board certified in internal medicine and sports medicine with additional training in hormone replacement therapy and regenerative medicine. He has trained or practiced at leading institutions including the Hughston Clinic, Cooper Clinic, Steadman-Hawkins Clinic of the Carolinas, and Cenegenics. He currently practices in Columbus, Ohio at Grandview Primary Care. Read more about Dr. Joe Jacko

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