What is Ketosis? Is It Safe?

Ketosis has become a prevalent issue recently, and it’s received its share of both praise and criticism. Is it healthy or dangerous to be in ketosis? And if it’s beneficial, should everyone be doing it?

Ketosis is a natural metabolic state.

It affects the body producing ketone bodies out of fat and using them for energy instead of carbs.

You can get into ketosis by following a particularly low-carb, high-fat ketogenic diet.

In addition to quick weight loss, ketosis has several health benefits like decreased seizures in epileptic children.

Some people promote ketosis by following a diet called the ketogenic or keto diet. This diet intends to burn unwanted fat by making the body rely on it for energy, rather than carbs.

Ketosis also occurs in people with diabetes, as it happens if the body does not have enough insulin or misusing it.

Health problems linked with extreme ketoses, such as diabetic ketoacidosis (DKA), are more likely to happen in people with type 1 diabetes.

In this guide, you’ll get all the information you need about ketosis. This includes its benefits, potential risks, and tips for successfully getting into ketosis:

What is Ketosis?

Ketosis is a metabolic condition in which fat provides most of the fuel for the body.

There is limited access to glucose (blood sugar), which serves as a fuel source for the body.

Ketosis is most often linked with ketogenic and very low-carb diets. It also happens during pregnancy, infancy, fasting, and starvation.

To go into ketosis, people generally need to eat fewer than 50 grams of carbs per day and sometimes as little as 20 grams per day.

This requires removing certain food items from your diets, such as grains, candy, and sugary soft drinks. You also have to cut back on legumes, potatoes, and fruit.

When doing a very low-carb diet, insulin levels go down and fatty acids are released from body fat stores in large amounts.

Many of these fatty acids go to the liver, where they are oxidized and turned into ketones (or ketone bodies). These molecules can provide energy for the body.

Unlike fatty acids, ketones can cross the blood-brain barrier and provide energy for the brain in the absence of glucose.

In normal circumstances, the body’s cells use glucose as the primary energy source. People can typically receive glucose from dietary carbs, including sugars and starchy foods.

The body breaks these down into simple sugars. Afterward, it both utilizes glucose as fuel or stores it in the liver and muscles as glycogen.

If there is not enough glucose available to produce enough energy, the body will adopt an alternative strategy to meet those needs. Specifically, it begins to split down fat stores and use glucose from triglycerides.

Ketones are a byproduct of this process. These are acids that build up in the blood and leave the body in the urine. In small amounts, they show that the body is breaking down fat. However, high levels of ketones can harm the body, leading to a condition called ketoacidosis.

Although both fasting and a keto diet will allow you to achieve ketosis, only a keto diet is sustainable over long periods. It appears to be a healthy way to eat that people can potentially follow indefinitely.

Keto Diet

Ketosis is a popular low-carb weight loss program. In addition to supporting you burn fat, ketosis can make you feel less hungry. It also helps you keep muscle.

For healthy people who don’t have diabetes and aren’t pregnant, ketosis kicks typically in after 3 or 4 days of eating less than 50 grams of carbohydrates per day. That’s around three slices of bread, a cup of low-fat fruit yogurt, or two small bananas. You can start ketosis by fasting, too.

A diet high in fat and protein but deficient in carbs is described as a ketogenic or “keto” diet.

As ketosis breaks down fat stores in the body, some keto diets aim to promote weight loss by creating this metabolic state.

Keto diets are usually high in fat. For instance, 20% of the calories may be protein, 10% may be carbs, and 70% may come from fat.

However, there are different versions. The nutrient proportions will depend on the version of the diet a person follows.

Following the keto diet can lead to short-term weight loss. This is partly because people are usually able to consume fewer calories without feeling hungry:

Benefits of Ketosis

Ketones provide sustainable energy. It produces BHB, in particular, which can reduce inflammation and oxidative stress. Hence, it helps reduce the risk of developing chronic diseases.

Here are other benefits of being in nutritional ketosis.

Established benefits:

  • Appetite regulation: One of the first things people often notice when they’re in ketosis is that they’re no longer hungry all the time. Research has shown that being in ketosis suppresses appetite.
  • One study looked at people who lost weight by following a ketogenic diet for eight weeks and then reintroduced small amounts of carbs. The researchers reported that ghrelin (the “hunger hormone”) was suppressed in those who remained in ketosis. Meanwhile, those who were no longer in ketosis had higher ghrelin levels.
  • Weight loss: Many people automatically eat less when they restrict carbs and are allowed as much fat and protein as they need to feel full. Because the ketogenic diet suppresses appetite, decreases insulin levels, and burns fat, it isn’t surprising it outperforms other diets intended for weight loss.
  • Reversal of diabetes and pre-diabetes: In pre-diabetic or have type 2 diabetes, ketosis normalizes blood sugar and insulin response. This can lead to discontinuation of diabetes medication.
  • Potentially enhanced athletic performance: Ketosis may provide an extremely stable fuel supply during sustained exercise in high-level and recreational athletes.
  • Seizure management: Maintaining ketosis with the classical ketogenic diet or less stringent Modified Atkins Diet (MAD) is proven effective for controlling epilepsy in children and adults who don’t respond to anti-seizure medication.

There are also researches suggesting that ketosis is beneficial for the following condition:

Although higher-quality research is needed to confirm these effects, much of the early research is very encouraging.

Does the Brain Need Carbs?

It’s a common misunderstanding that the brain doesn’t function without dietary carbs.

It’s true that glucose is preferred and that some cells in the brain can only use glucose for fuel.

However, a large part of your brain uses ketones for energy, mostly when you’re hungry or in a low-carb diet.

In fact, after only three days of hunger, the brain gets 25% of its energy from ketones. During long-term starvation, this number rises to around 60%.

There’s a long-standing yet misguided belief that carbs are necessary for proper brain function.

If you ask some dietitians how many carbs you should eat, they’ll likely respond that you need a minimum of 130 grams per day. This is to ensure that your brain has a steady supply of glucose.

However, this isn’t the case. Your brain will remain healthy and functional, even if you don’t eat any carbs at all.

Although it’s true that your brain has high energy demands and requires some glucose, ketones can help supply that demand. Moreover, your liver will always make small amounts of glucose your brain needs, even while fasting.

This process, known as gluconeogenesis (literally “making new glucose”), provides glucose to other parts of the body where it’s needed. This process allowed our hunter-gatherer ancestors to go for long periods without eating. That’s because stored body fats serve as the body’s fuel source.

In truth, being in ketosis doesn’t have any adverse effects on brain function. On the contrary, many people have reported that they feel sharper mentally when they’re in ketosis.

Also, your body can use protein to produce the little glucose the brain still requires during ketosis. This process is called gluconeogenesis.

Ketosis and gluconeogenesis are quite capable of meeting the brain’s energy needs.

Ketoacidosis: Treatment and Prevention

People often confuse ketosis and ketoacidosis. While ketosis is part of regular metabolism, ketoacidosis is a dangerous metabolic condition that can be fatal if left untreated.

In ketoacidosis, the bloodstream is flooded with too high glucose (blood sugar) and ketones.

When this happens, the blood becomes acidic, which is incredibly harmful.

Ketoacidosis is most often associated with uncontrolled type 1 diabetes. It may also happen in people with type 2 diabetes, although this is less common.

Also, severe alcohol abuse may lead to ketoacidosis.

Ketosis does not usually happen in people who eat balanced diets and regular meals. Reducing calorie and carb intake, exercising for extended periods, and pregnancy can trigger ketosis.

Although some people choose to put the body through ketosis, the chance of increased acid levels can be dangerous in those who are not controlling it.

In people with diabetes, ketosis and DKA can occur if they do not use sufficient insulin, skip meals, or an insulin reaction. An insulin reaction usually happens while asleep.

Doctors consider DKA an emergency, as it can point to a diabetic coma and even death. Emergency healthcare workers will usually administer treatment followed by hospitalization in an intensive care unit.

For those with diabetes, the emergency team will regularly take the following measures:

  • Fluid replacement: Doctors use this method to rehydrate the body and dilute the blood’s excess sugar.
  • Electrolyte replacement: This helps a person sustain heart, muscle, and nerve cell function. Levels in the blood often drop in the lack of insulin.
  • Insulin therapy: This can help doctors reverse the processes that led to ketoacidosis.

If you’re a healthy person, a healthy, balanced diet and regular exercise can prevent ketosis.


There are numerous ways a person with diabetes can prevent ketoacidosis, including:

  • Carefully observing their blood sugar levels at least three to four times per day
  • Managing insulin dosage with a specialist
  • Following a diabetes treatment plan

People with diabetes should keep an eye on their ketone levels with a test kit, especially when ill or under stress.

Negative Effects of Ketosis

There are a few possible side effects you may experience from ketosis and ketogenic diets.

These include headache, fatigue, constipation, high cholesterol levels, and bad breath.

However, most of the symptoms are temporary and should pass within a few days or weeks. Also, some epileptic children have developed kidney stones while on a diet.

And although very rare, there have been a few cases of breastfeeding women developing ketoacidosis. A low-carb or ketogenic diet likely triggers this.

People taking drugs that help lower blood sugar should consult with a doctor before attempting a ketogenic diet. That’s because the diet may reduce the need for medication.

Sometimes ketogenic diets are low in fiber. For this reason, it is a good idea to make sure to eat plenty of high-fiber, low-carb vegetables.

All that being said, ketosis usually is safe for healthy people.

Nevertheless, it will not suit everyone. Some people may feel great and full of energy in ketosis, while others feel miserable.

Signs and Symptoms That You’re In Ketosis

The ketogenic diet is a popular, effective way to lose weight and enhance your health.

When done correctly, the low-carb high-fat diet can increase blood ketone levels.

These provide a new fuel source for your cells and produce most of this diet’s unique health benefits.

On a ketogenic diet, your body undergoes many biological changes. This includes a decrease in insulin levels and increased fat breakdown.

When this happens, your liver starts creating high numbers of ketones to supply energy for your brain.

However, it can often be hard to identify whether you’re in ketosis or not.

Here are the common signs and symptoms of ketosis, both positive and negative.

Bad Breath

People frequently report bad breath once they reach full ketosis.

It’s a common side effect. Many people on ketogenic diets and similar diets, such as the Atkins diet, report that their breath takes on a fruity odor.

Elevated ketone levels cause this. The particular culprit is acetone, a ketone that exits the body in your urine and breath.

While this breath may be less than ideal for your social life, it can be a positive indication for your diet. Many ketogenic dieters brush their teeth many times per day or use sugar-free gum to solve the issue.

If you’re using gum or other options like sugar-free drinks, check the label for carbs. These may raise your blood sugar levels and reduce ketone levels.

Weight Loss

Ketogenic diets, along with regular low-carb diets, are highly useful for weight loss.

As dozens of weight loss studies have shown, you will likely experience both short- and long-term weight loss when turning to a ketogenic diet.

Fast weight loss can occur throughout the first week. While some people believe this to be fat loss, it’s essentially stored carbs and water being used up.

After the first rapid drop in water weight, you should be able to keep on losing body fat. More so, if you stick to the diet and remain in a calorie deficit.

Increased Ketones in the Blood

One of the trademarks of a ketogenic diet is reducing blood sugar levels and an increase in ketones.

As you proceed further into a ketogenic diet, you will start to burn fat and ketones as the primary fuel sources.

The most secure and accurate method of measuring ketosis is to measure your blood ketone levels using a specialized meter.

It calculates your ketone levels by measuring the amount of beta-hydroxybutyrate (BHB) in your blood.

This is one of the primary ketones present in the bloodstream.

According to some experts on the ketogenic diet, nutritional ketosis is characterized as blood ketones ranging from 0.5–3.0 mmol/L.

Measuring ketones in your blood is the most reliable way of testing and is used in most research studies. However, the main downside is that it requires a small pinprick to draw blood from your finger.

Increased Ketones in the Breath or Urine

Another way to determine blood ketone levels is a breath analyzer.

It monitors acetone, one of the three primary ketones already in your blood during ketosis.

This gives you an idea of your body’s ketone levels since more acetone exits the body when you are in nutritional ketosis.

The use of acetone breath analyzers is reasonably accurate, though less accurate than the blood monitor method.

Another useful technique is to measure the presence of ketones in your urine daily with unique indicator strips.

These also measure ketone discharge through the urine and can be a quick and cheap method to assess your ketone levels each day. 

Appetite Suppression

Many people report reduced hunger while following a ketogenic diet.

The reasons why this happens are still being investigated.

However, it’s been suggested that this hunger reduction may be due to an increased protein and vegetable intake, along with alterations to your body’s hunger hormones.

The ketones themselves may also influence your brain to reduce appetite.

Increased Focus and Energy

People usually report brain fog, tiredness, and feeling sick when first starting a very low-carb diet. This is called the “low carb flu” or “keto flu.” However, long-term ketogenic dieters often state increased focus and energy.

When you start a low-carb diet, your body must adjust to burning more fat for fuel instead of carbs.

When you get into ketosis, a large part of the brain begins burning ketones instead of glucose. It can take a few days or weeks for this to start working correctly.

Ketones are a beneficial fuel source for your brain. They have even been tested in a medical context to treat brain diseases and conditions such as concussion and memory loss.

Therefore, it’s not surprising that long-term ketogenic dieters often report enhanced clarity and improved brain function.

Eliminating carbs can also help control and stabilize blood sugar levels. This may significantly increase focus and improve brain function.

Short-Term Fatigue

The primary switch to a ketogenic diet can be one of the most significant issues for new dieters. Its well-known side effects can involve weakness and fatigue.

These often cause people to quit the diet before they get into full ketosis and reap many long-term gains.

These side effects are natural. After several decades of running on a carb-heavy fuel system, your body is forced to adjust to a different approach.

As you might expect, this switch doesn’t happen overnight. It generally requires 7–30 days before you are in full ketosis.

To reduce fatigue while transitioning, it would be best to take electrolyte supplements.

Electrolytes are often lost because of the fast reduction in your body’s water content. It also has something to with removing salty, processed food from your diet.

When adding these supplements, try to get 2,000–4,000 mg of sodium, 1,000 mg of potassium, and 300 mg of magnesium each day.

Short-Term Decreases in Performance

As discussed above, eliminating carbs can lead to general tiredness at first. This includes an initial drop in exercise performance.

It’s primarily caused by the decrease in your muscles’ glycogen stores. This provides the primary and most efficient fuel source for all forms of high-intensity exercise.

After several weeks, many ketogenic dieters report that their performance recovers to normal. In certain types of ultra-endurance sports and events, a ketogenic diet could even be helpful.

What’s more, there are further benefits — essentially an increased ability to burn more fat during exercise.

According to one study, athletes who switched to a ketogenic diet burned up to 230% more fat when they exercise. 

While it’s unlikely that a ketogenic diet can spike performance for elite athletes, it should be enough for general exercise and recreational sports once you become fat-adapted.

Digestive Issues

A ketogenic diet usually includes a significant change in the types of foods you eat.

Digestive issues such as constipation and diarrhea are common side effects in the beginning.

Some of these issues should subside after the transition period. Nonetheless, you should be mindful of different foods that may be causing digestive problems.

Also, make sure to eat plenty of healthy low-carb veggies low in carbs but still hold plenty of fiber.

Most importantly, don’t make the error of eating a diet that lacks diversity. Doing that may increase your risk of digestive issues and nutrient deficiencies.


One big concern for many ketogenic dieters is sleep, especially when they first change their diet.

A lot of people report insomnia or waking up at night when they first reduce their carbs dramatically.

However, this usually improves in a matter of weeks.

Many long-term ketogenic dieters insist that they sleep better than before after adapting to the diet.

Tips for Getting Into Ketosis

There are several ways you can get into nutritional ketosis safely and effectively.

  • Reduce daily net carb intake to less than 20 grams: Though you may not need to be this strict, eating fewer than 20 grams of net carbs every day allows you to achieve nutritional ketosis.
  • Try intermittent fasting: Going for 16-18 hours without eating may help you get into ketosis more quickly.
  • This is easy to do by merely skipping breakfast or dinner, which may feel very natural on an appetite-suppressing keto diet.
  • Don’t fear fat: Eating plenty of fat is a necessary and delicious part of ketogenic eating! 
  • Make sure to include a source of healthy fat at each meal.
  • Cook with coconut oil: Besides being a natural fat that remains stable at high heat, coconut oil contains medium-chain fatty acids. This kind of fatty acids can boost ketone production.
  • Exercise, if possible: During the transition into ketosis, you may not have enough energy to engage in vigorous physical activity. However, going for a brisk walk may help you get into ketosis more quickly.

Is Being in Ketosis Safe for Everyone?

Being in ketosis is safe for most people, and it can provide many health benefits. This includes weight loss, optimal blood sugar, and insulin levels, to name a few.

However, specific individuals should only follow a ketogenic diet under medical supervision. And others are best off avoiding it altogether.

Conditions that require medical supervision and monitoring during ketosis:

  • Type 1 diabetes
  • Type 2 diabetes on insulin or oral diabetes medications
  • High blood pressure on medication
  • Liver, heart, or kidney disease
  • History of gastric bypass surgery
  • Pregnancy

Conditions for which ketosis should be avoided:

  • Breastfeeding women
  • Individuals with rare metabolic conditions (i.e., enzyme deficiencies)


Several vital signs and symptoms can help you distinguish whether you are in ketosis.

Ultimately, if you’re obeying ketogenic diet guidelines and stay consistent, you should be in some form of ketosis.

If you want a more accurate assessment, monitor ketone levels in your blood, urine, or breath every week.

That being said, if you’re losing weight, enjoying your ketogenic diet, and feeling healthier, there is no need to hound over your ketone levels.

Ketosis happens when the body starts to obtain energy from stored fat instead of glucose.

Many studies have shown the powerful weight loss effects of a low carb or keto diet. However, this diet can be challenging to maintain and may cause health problems in people with certain conditions, such as type 1 diabetes.

DKA is a particularly threatening complication of ketosis that can occur when ketosis makes the blood too acidic. Emergency treatment is necessary for people experiencing DKA.

Most people can try the keto diet safely. However, it is best to consider any significant changes to diet with a dietitian or doctor. This is especially the case in those with underlying conditions.