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Ketosis: Symptoms, Benefits, Risks, and More


What is Ketosis?

Ketosis is a natural state wherein your body metabolizes its stored fat to produce energy instead of glucose from your diet. During ketosis, the levels of beta-hydroxybutyrate or BHB ketones in your blood increase to 0.5-3 mmol/L (*).

It’s important to note that the liver continually produces a small number of ketones even when you’re eating more carbs, and these low ketone levels do not cause problems. However, in the absence of carbs, increased ketones can be beneficial in that they now serve as your fuel source — on top of reducing inflammation in the body (*).

To achieve ketosis and experience the possible advantages, an individual can follow different approaches, with a popular one being the ketogenic diet. Others that may be used alone or in combination with the keto diet include intermittent fasting and exercises that deplete glycogen fast.

Ketosis Symptoms

There are many ways to tell you’re in ketosis. Watch out for these temporary signs and symptoms, which occur within a few days (usually 3-4 days) of reducing carbs to less than 50 grams:

  • Bad breath: Also known as keto breath, this bad breath is often described as fruity-smelling, which is similar to nail polish remover. Acetone is an ingredient in nail polish removers and it’s also one of the chemicals that increase in your body during ketosis — which explains the resemblance.
  • Losing water weight: Restricting carbs leads to an initial weight loss, which is usually rapid. This early weight loss is mostly water weight since increased carb intake causes water retention. A more gradual fat loss happens as the person adheres to the keto diet.
  • Fatigue: Feeling more tired is another common complaint as your body tries to switch from glucose to ketones for energy. This weakness eventually resolves and you can reduce it by taking electrolytes.
  • Increased ketones (blood, urine, and breath): Testing for ketones — using a blood ketone meter, urine test strip, or breath acetone meter — shows higher ketone readings. Among the three testing methods, the blood monitor is the most reliable because it directly measures BHB, the most abundant ketone.
  • Digestive issues: Diarrhea or constipation is also a side effect of ketosis. Diarrhea can be caused by a high fat intake (since dietary fats replace carbs) while constipation can result from low amounts of fiber (since cutting carbs can mean removing many plant foods like quinoa, oats, and apples).
  • Insomnia: Interrupted sleep happens shortly after reducing carbs. Possible reasons for keto insomnia include low blood glucose and electrolyte imbalances, which can be managed through gradual carb reduction, eating your carbs for later in the day, and electrolyte supplementation.
  • Decreased athletic performance: Removing carbs from your diet will deplete your muscle glycogen stores, which may lead to decreased performance in the gym (*). This is especially true for high-intensity workouts.
  • Sore muscles: It is also possible to experience body aches and cramps, which happen due to a lack of electrolytes. Fewer carbs make your body flush out more water, along with a loss of some electrolytes like sodium and potassium.
  • Sugar cravings: Keto helps control sugar cravings, although it’s important to remember that these cravings increase when you’re just starting out. Being highly dependent on carbs in the past may trigger intense cravings when you remove them.

These symptoms of ketosis are collectively called the keto flu — because they resemble symptoms of the flu. Although they’re almost inevitable, they resolve on their own and can be successfully managed through optimal nutrient intake, hydration, and rest.

Potential Health Benefits of Ketosis

The benefits of ketosis can range from weight loss to potentially improved exercise performance and better metabolic health markers, according to studies. These may be attributed to the reduction of body fat, blood sugar control, and the therapeutic effects of ketones.
Here are some of the research-backed benefits of being in ketosis:

  • Appetite suppression: Many people notice a reduction in their appetite days after starting the keto diet. Research has found that ketogenic diets prevent an increase in ghrelin, a hormone produced by the stomach that makes you feel hungry (*).
  • Fat loss: Reduced hunger during ketosis leads to eating less food, which results in fat loss. In fact, when comparing low-carb versus low-fat diets, those in low-carb groups end up losing more weight (*, *)
  • Fewer seizures: Children and adults diagnosed with epilepsy can follow a classic keto diet if their seizures are not effectively controlled by medications. Studies have shown evidence that ketones can have significant anti-seizure effects, and that exogenous ketone supplementation may provide some benefit in addition to a keto diet (*).
  • Type 2 diabetes reversal: Those with type 2 diabetes can achieve reversal — meaning the condition is controlled and their blood sugar stays below diagnostic thresholds — using nutritional ketosis. Patients who maintain a very low-carb diet with the guidance of a qualified health professional are able to improve their HbA1c in two weeks (*).
  • Reduced heart disease risk: Keeping your blood sugar levels under control may ultimately benefit your heart health. Research shows that hyperglycemia can cause triglycerides to increase, which contributes to the thickening of artery walls (*).
  • Brain health: Besides helping with unmanaged epilepsy, ketosis may benefit individuals who have Alzheimer’s disease (the most common form of dementia) and traumatic brain injury by protecting brain cells and providing an alternative fuel for the brain (*, *).
  • Improved endurance: While cutting carbs makes you feel tired and unable to sustain a workout in the beginning, you eventually reach keto-adaptation. This happens when your body stays long enough in ketosis that it acclimates to utilizing ketones as its main fuel. Research has shown that keto-adapted elite race walkers who adhered to a low-carb diet had better endurance capacity (*).
  • Cancer prevention and therapy: There’s also research suggesting that keto may help fight cancer by increasing ketones and reducing calories. Interestingly, cancer cells cannot use ketones for energy (*).  Examples of cancers that keto may help with include glioblastoma, colon cancer, pancreatic cancer, breast cancer, and colorectal cancer.

Ketosis vs. Ketoacidosis

Ketosis is a natural metabolic process and it’s generally safe for healthy individuals and patients under the supervision of a qualified professional, whereas ketoacidosis is a medical emergency (*). While both states involve ketone production, ketone levels during ketoacidosis increase to dangerous levels, in addition to very high blood sugar.

Ketoacidosis, also known as diabetic ketoacidosis (DKA), is a complication among individuals with type 1 diabetes who often miss their insulin shots. Having an illness or infection can also increase the risk of ketoacidosis.

ketosis vs ketoacidosis

How to Get Into Ketosis

Reaching ketosis can be done using different strategies, but for the most part, it involves lowering your carbohydrate intake to 20-50 grams each day. The easiest way to meet this carb requirement is to focus on non-starchy vegetables and fruits, such as broccoli, brussels sprouts, spinach, cucumber, avocados, berries, and melons.

Since most meats and seafood have next to zero or zero carbs, you can have them in abundance. Animal-based foods are healthy sources of fat, which helps absorb vitamins and produce hormones, in addition to keeping you satisfied and full while you’re reducing carbs.

Tip: Follow the recommended keto macros based on your goals. In case you don’t know them yet — use our free Perfect Keto macro calculator.

Exercise is another useful tool to enter ketosis. The longer and more intense the workout, the sooner your glycogen stores become depleted (*). If you feel a lack of energy to exercise due to the keto flu, try a lighter exercise, such as brisk walking or yoga. As soon as you feel better, resume your usual workouts.

Intermittent fasting, whether done alone or in combination with exercise, can also speed up ketosis. In fact, research shows that abstaining from eating for periods may be effective in decreasing hunger, which can boost weight loss while on a keto diet (*).

How Long Does It Take to Get Into Ketosis?

If you consume only 50 grams of carbs per day or even lower, you will likely enter ketosis in a matter of 3-4 days. Do keep in mind that the time to enter ketosis may vary from one individual to another depending on different factors.

So, other than a person’s carb intake, factors that may influence ketosis include metabolism (a faster metabolism burns energy more quickly), physical activity, fasting, sleep, and stress levels. While implementing all the necessary steps to achieve ketosis — don’t forget to test your ketone levels.

Ketosis and the Ketogenic Diet

The ketogenic or keto diet is designed to help your body utilize ketones as its main fuel source instead of glucose. In other words, it’s intended to stimulate ketosis. The way it does this is by reducing carbs to just 30-50 grams each day.

In addition to being low in carbs, the keto diet is high in fat and moderate in protein. Standard keto diet macros are as follows (*):

  • 5-10% carbohydrates
  • 30-35% protein
  • 55-60% fat

As you’ve learned in this guide, the keto diet is not the only method of reaching ketosis. Simply cutting carbs can decrease your glycogen stores; however, optimizing your intake of fat and protein will ensure that you have enough for your energy and health requirements.

What is Optimal Ketosis?

The target ketone level for ketosis ranges from 0.5-3 mmol/L. This range is also ideal for experiencing weight loss. Just note that a qualified healthcare professional should supervise people with diabetes who are on a keto diet. This is because diabetes requires blood glucose monitoring, especially with increasing ketone levels to prevent diabetic ketoacidosis.

Check out this detailed guide on testing ketone levels and what they mean.

Potential Risks & Side Effects of Ketosis

Common ketosis side effects include symptoms that resemble the flu, such as weakness, bad breath, digestive issues, insomnia, and muscle soreness. They happen when you start the keto diet, but they go away after a few weeks or a month of being consistent with keto.

Less common side effects and potential risks include the following:

  • Hypotension: Abnormally low blood pressure can occur if a person with hypertension takes blood pressure-lowering medication while doing low-carb. Although keto lowers blood pressure, which is good news, it needs to be discussed with a healthcare provider in case medication adjustments are necessary.
  • Hypoglycemia: Abnormally low blood glucose is another risk when you’re avoiding carbs while taking insulin and other glucose-lowering medications. This is why people with diabetes should test their blood glucose more often at the start of the keto diet.
  • Nutrient deficiency: Nutritional deficiencies can happen only when you fail to replace those high-carb, nutrient-dense foods with low-carb versions. What’s great about filling up on meat and seafood, which have almost zero carbs, is that they’re by far the most nutrient-rich foods on the planet.

Is Ketosis Safe for Everyone?

In most cases, ketosis is considered safe and beneficial for preventing and managing health conditions, although it requires medical supervision — especially for those taking blood sugar and blood pressure medications. Also, it’s important to be aware of some of the short-term side effects of ketosis, such as fatigue and other keto flu symptoms, so that you can prepare for them.

The Bottom Line

Ketosis is a natural process and is characterized by increased ketone levels. Instead of glucose, your body uses ketones for fuel. You’ve learned that ketosis has many benefits, from suppressing appetite (which leads to weight loss) to preventing certain cancers.

When it comes to reaching ketosis, a healthy way to do it is by following the keto diet, which is very low-carb, high-fat, and moderate-protein. Other strategies that can be implemented while on keto to speed up ketosis include exercising and intermittent fasting.

Remember to consult a healthcare provider who can help create a personalized keto plan that supports your goals and keeps you healthy!

17 References

Victoria M. et al. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. 2018 September

Hubert K. et al. Ketone bodies: from enemy to friend and guardian angel. 2021 December 9

Bob M. et al. Fundamentals of glycogen metabolism for coaches and athletes. 2018 February 10

Sarah E. et al. Impact of ketosis on appetite regulation. 2020 May

Frederick F. et al. A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity. 2003 May 22

Gary D. et al. A Randomized Trial of a Low-Carbohydrate Diet for Obesity. 2003 May 22

Angela M. et al. Ketone Administration for Seizure Disorders: History and Rationale for Ketone Esters and Metabolic Alternatives. 2019 October 15

Virta Health. Reversing Type 2 Diabetes: An Evidence-Based Guide

Hirano T. et al. Effect of acute hyperglycemia on plasma triglyceride concentration and triglyceride secretion rate in non-fasted rats. 1990 July

Samuel T. et al. Study of the ketogenic agent AC-1202 in mild to moderate Alzheimer’s disease: a randomized, double-blind, placebo-controlled, multicenter trial. 2009 August 10

Alexandre Mc. et al. The ketogenic diet as a treatment for traumatic brain injury: a scoping review. 2018

Sihui M. et al. Keto-Adaptation and Endurance Exercise Capacity, Fatigue Recovery, and Exercise-Induced Muscle and Organ Damage Prevention: A Narrative Review. 2019 February.

Poff A. et al. Ketone supplementation decreases tumor cell viability and prolongs survival of mice with metastatic cancer. 2014 February 26

Centers for Disease Control and Prevention. Diabetic Ketoacidosis. 2022 December 30

Bob M. et al. Fundamentals of glycogen metabolism for coaches and athletes. 2018 February 10

Eric R. et al. Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. 2019 August

Wajeed M. et al. Ketogenic Diet. 2022 June 11


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