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Home arrow Nutrition arrow Keto Diet arrow How Long Is It Safe to Be in Ketosis? Side Effects and Benefits

How Long Is It Safe to Be in Ketosis? Side Effects and Benefits

Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: September 28, 2023
7 min read 1010 Views 0 Comments
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The keto diet is one of the most popular ways to lose weight. But you need to know how long to stay in ketosis to avoid unpleasant side effects.

how long is it safe to be in ketosis

If eating carbs isn’t your favorite thing, the keto diet could be just right for you. This high-fat diet limits your carbohydrate intake and makes your body burn fat for energy, a process known as ketosis.

Getting into ketosis takes as little as a few days. According to most studies, you can then stay in ketosis for a few months without adverse health effects.

Read on to find out just how long it’s safe to be in ketosis and what exactly happens to your body during this state.

How Long Is It Safe to Be in Ketosis?

Being in ketosis is safe for as long as 6 months, according to a scientific study on the long-term effects of the keto diet on obese people.

Other research found that inflammation and other side effects may occur in mice after 12 weeks of being on this low-carb diet.

Keto eating for several months appears to be healthy. However, more extended research studies are needed to support following a long-term ketogenic diet.

What Is Ketosis?

Ketosis is the metabolic state that occurs when your body starts using fats instead of carbs as its main source of energy. The body breaks down stored fat and fatty acids in the liver.

This creates ketone bodies in the bloodstream. Ketone bodies are metabolites that your body burns for fuel instead of glycogen, which it converts from carbs.

You can force your body into ketosis by following a ketogenic diet. Also known as a keto diet, this is a low-carb eating plan that consists of 70% fat, 25% protein, and 5% carbs.

It has been used to treat children with epilepsy for more than 100 years. It has also been successfully used in the US military to achieve serious weight loss, including the loss of unhealthy visceral fat, without decreasing physical performance.

You can get into ketosis in as little as 24 hours, but that calls for cutting carbs entirely and fasting completely.

If you begin to follow a ketogenic diet at a more relaxed pace, your body may go through an adaptation phase that takes at least several days. Ketosis occurs after this adaptation phase, but only if you carefully follow keto eating guidelines.

The early signs of ketosis are quite noticeable and may include decreased appetite, bad breath, higher blood ketone levels, weight loss, and sleep changes. Once your body enters ketosis, you burn fat at a higher rate than usual.

It’s possible to be in ketosis but not lose weight. To see results, you have to make sure this low-carb diet is suitable for you and follow it carefully for at least 3 months. 

But before you embark on a keto diet plan, it’s important to understand just how long you can do it.

The bottom line is that how long you follow a keto plan shouldn’t depend on your weight loss results. Rather, switch from low-carb eating to a normal diet within a few months before your body can experience the long-term consequences of this diet.

You can later return to keto eating to take advantage of the fat-burning stage of ketosis. But bear in mind that this diet is not necessarily a low-calorie diet. Fats have more than twice as many calories as carbs.

5 Possible Side Effects of Ketosis

Ketosis brings with it several side effects you should know about before embarking on a keto diet. These side effects range from mild to serious.

#1 Keto flu

When your body starts burning fat for energy, you may experience flu-like symptoms, including headaches, tiredness, cramps, and nausea.

This is known as the keto flu and typically lasts only a few days. While unpleasant, keto flu is a sign that your body is entering ketosis.

#2 Digestive problems and heartburn

Your body has to work harder to digest fats than carbs, and on keto, you’re feeding it more fats than usual. This can lead to abdominal discomfort, heartburn, diarrhea, constipation, and other digestive problems.

On the plus side, a recent study suggests that keto eating can increase beneficial bacteria in the gut.

#3 Kidney stones

Kidney stones are one of the most often cited keto diet long-term side effects. Eating animal protein increases urine acidity and calcium levels. These may lead to a gradual buildup of kidney stones.

A review of 36 studies found that the incidence of kidney stones in keto dieters was 5.9% for children and 7.9% for adults.

Eating calcium-rich foods can protect you from kidney stones. You can also add lemon juice to your water for a healthy dose of citrate that decreases the risk of kidney stones.

#4 Bone density loss

A study on elite race walkers found that following a keto diet for just a few weeks decreased bone metabolism and formation markers while increasing bone breakdown. A higher risk of fractures has also been noted in children fed this diet as part of their epilepsy treatment.

#5 Nutrient deficiencies

A keto diet that is not carefully formulated puts you at an increased risk of suffering nutrient deficiencies. These deficiencies may include vitamins A, D, and E and the micronutrients selenium and magnesium, all of which the body needs to stay healthy.

3 Benefits of Ketosis

Side effects aside, ketosis brings a series of notable benefits. These make keto one of the most popular diets for losing weight.

#1 Weight loss

Several studies support the ketogenic diet as a way to shed excess pounds.

First, it dramatically reduces the number of carbs you eat. Your total carb intake is one of the factors determining your body mass index. Carbs also impact your blood glucose levels. Cutting back carbs can decrease blood sugar.

Secondly, it forces your body to burn ketones derived from fat as its main energy source. This can lead to a significant reduction in your body’s fat percentage, including harmful visceral fat.

#2 It makes you feel full for longer

Keto eating can also reduce hunger. Fats can make your stomach feel fuller for longer.

A review of several studies has noted the appetite-suppressing effect of being in ketosis. The mechanism behind this is not fully understood. But it seems that ketosis leads to the release of satiety peptides.

#3 May improve cardiovascular health

Keto eating means consuming mostly fats. So it may seem counterintuitive that the keto diet can improve heart health.

But when you follow a healthy keto plan, you can replace saturated fats with plant-based fats such as avocados and healthy oils.

According to several animal and human studies, this can lead to a decrease in bad LDL cholesterol levels and triglycerides. These are associated with stroke and cardiovascular disease.

For Who Is It Not Recommended to Follow a Ketogenic Diet?

As we’ve seen, the keto diet has some notable health benefits beyond weight loss.

However, a keto diet plan can be harmful to people with certain existing medical conditions. High ketone levels and a high fat intake can have a worsening effect on a range of common conditions.

Avoid ketogenic eating if you have one or more of the following conditions:

  • Type 1 diabetes. For people living with type 1 diabetes, eating keto can lead to a life-threatening complication – diabetic ketoacidosis. In this, a buildup of ketones in the blood can poison the body and require immediate medical attention.
  • Type 2 diabetes. Eating keto means eating plenty of fats, which may include fats from meat and dairy products. These can raise bad cholesterol levels beyond healthy limits and increase the risk of cardiovascular disease.
  • Cardiovascular disease. Keto is high in fat, which is not ideal if you have existing cardiovascular health issues. It may elevate LDL cholesterol and triglyceride levels, both of which are risk factors for heart disease.
  • Hypothyroidism. Sticking to a keto meal plan can lower thyroid hormones, which can lead to hypothyroidism complications.
  • Chronic kidney disease. Following a keto diet can also worsen kidney disease. Ketosis increases ketone levels in the urine. This causes a buildup of acid in the urine, which weakened kidneys cannot remove efficiently.
  • Gallbladder disease. The gallbladder plays a key role in supporting the digestion of fat. People with damaged or removed gallbladders may struggle on a keto diet.
  • Eating disorders. Similar to other demanding eating plans, a keto plan could cause disordered eating in people susceptible to this.

Important: The high-fat, low-carb keto diet is not suitable for pregnant women.

Before you start following a keto plan, you may want to talk with a doctor or registered dietitian. This is especially important if you have any existing medical conditions.


Is ketosis safe?

Ketosis is safe for keto dieters without pre-existing medical conditions for up to several months. Not only is it safe in the short term, but several studies have highlighted its weight loss benefits.

How long does it take to see results from keto?

Keto dieters may start seeing results after 2–6 weeks after the keto-adaptation period ends. Some people on a ketogenic diet see results faster than others.

How long does it take to get into ketosis?

You can get into ketosis in as little as 3–4 days with the right meal plan and intermittent fasting. How fast you enter ketosis depends on your meal plan as well as on your body composition and genes.

A Word From a Nutritionist

Although it may sound counterintuitive, a high-fat diet could help you lose weight. A solid body of scientific evidence supports the ketogenic diet as an effective weight loss diet with other potential benefits.

More than reducing your intake of carbs, the keto diet can make you eat healthy fats.

For keto eating to work effectively, however, you need to follow a careful keto diet plan. Planning your meals is crucial to maintain the ratio of 70% fat, 25% protein, and 5% carbs.

Entering ketosis by starving yourself of carbs and staying in this state for more than a few months raises health concerns.

Keep your keto diet safe by following a keto plan reviewed by a nutritionist.

Key Takeaways

Before you get into ketosis, here are the key things to remember:

  • The keto diet increases your ketone levels and helps with losing weight fast.
  • It’s one of the safest and most effective short-term low-carb diets out there.
  • The keto diet plan can save you from having to keep a close eye on your calorie intake.
  • An effective keto diet plan consists of 70% healthy fats.
  • You need to track your carb count to maintain a low-carb intake.
  • Keto flu is a normal side effect of your body entering ketosis.
  • Follow a safe keto diet plan for losing weight without serious side effects.
  • While in ketosis, avoid eating unhealthy fats like animal fats and coconut oil in large quantities.
  • After keto dieting, keep eating healthy and with an eye on calories to prevent putting back on the lost weight.
Written by Edibel Quintero, RD
Edibel Quintero is a medical doctor who graduated in 2013 from the University of Zulia and has been working in her profession since then. She specializes in obesity and nutrition, physical rehabilitation, sports massage and post-operative rehabilitation. Edibel’s goal is to help people live healthier lives by educating them about food, exercise, mental wellness and other lifestyle choices that can improve their quality of life.
The article was fact checked by Rosmy Barrios, MD
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Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: September 28, 2023
7 min read 1010 Views 0 Comments

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