The keto diet is trending, no doubt about it. Those that have tried it rave about the rapid weight loss. 

Obesity continues to be a health problem in the world and runs hand in hand with heart disease, elevated cholesterol levels, and high blood pressure (6).

But you are here because the diet just sounds too good to be true, you are curious to know is keto dangerous? 

Every year there is a new trend that promises quick weight loss, also known as a fad diet.

Fad diets are usually restrictive diets that require modifying the number of carbohydrates, protein, or fat in varying levels. 

As a dietitian, talking about a fad diet can be difficult because the goal is always to recommend an individualized plan that is in balance.

Sometimes, dieters in extreme cases completely remove entire food groups from their diet. 

Follow a plan that requires calorie counting without considering the nutritional value of foods, generally lacking in moderation and leading to an unhealthy relationship with food.

These diet trends promise rapid weight loss but rarely talk about side effects. With any extreme restriction in a diet, an imbalance is bound to occur.

What Is the Keto Diet?

Keto diet

In the case of the ketogenic diet, also known as the keto diet, because it has been around for years it has well-documented success with weight loss. 

Studies have shown that short-term side effects of the keto diet up to 2 years are known, yet there aren’t many studies that show long-term side effects from being on a keto diet (6).

This diet restricts carbohydrate intake significantly, provides moderate protein and a higher fat intake (11). 

In this case, like any other diet that restricts or increases the three important macronutrients (carbs, protein, fat) adverse effects can be noted in varying degrees and depending on the individual.

The main research is on the ketogenic diet used in patients with epilepsy and for short periods of time.

The reality of the keto diet is that it has been around since 1920 and was originally used in the medical world as a therapeutic diet.

Used to treat and control seizures. 

But its use diminished with new antiepileptic medications (3).

A resurgent use of the diet has started to be used to moderate symptoms of children with epilepsy. Those that are resistant to antiepileptic medication (5).

 These patients are closely monitored by a medical doctor and clinical dietitian.

The clinical dietitian assesses the child and determines the percentage requirements of the macronutrients.

If you are following the keto diet for weight loss, chances are you have not gotten an assessment done by a registered dietitian. 

Therefore, you are online looking for the best keto meal plans, keto snacks, or keto recipes that people put out on their websites. But have you ever asked yourself, Is keto bad for you? 

If you have not already read about the diet, let me do a quick summary.

In general, the classic keto diet restricts carbohydrates down to 5-10% (between 20- 50 grams per day), a moderate intake of protein (which can be about 1 gram/kilogram of weight), and a high intake of fat (6).

By restricting carbohydrates to under 50 grams, you push your body to look for alternate sources of fuel, such as fat. 

When you start to burn fat, you produce ketone bodies and you enter into a state of ketosis.

Ketosis, known as a metabolic state, can result from fasting, extended exercising, and a very low carbohydrate diet. 

The liver identifies that the body is low on glucose (sugar) and shifts its focus on breaking down fat to use as energy leading to weight loss. 

Being in ketosis, your body produces ketones or ketone bodies in elevated levels and allows for the body to use fat as fuel. 

To know if you are in ketosis, you usually have bad breath, weight loss, increased ketones in the blood, increased ketones in the breathe or urine, appetite supression, increase focus and energy, fatigue or low energy for a short period of time. 

Yet, most concerning is that in the attempt to have a quick fix that provides results with short-term success, it’s possible to not take into account the long-term effects of a strict diet.

Here they are, the 7 dangerous side effects of a keto diet

1. Severe Hypoglycemia

A very low intake of carbohydrates can result in low blood sugar, known as hypoglycemia. If you are healthy you may get symptoms of fatigue,dizziness, confusion, slurred speech.

But if you have a medical condition such as diabetes you can have even more symptoms that can lead to loss of consciousness, seizures, and the inability to eat.

This can become a medical emergency that may need treatment (4).

A diagnosis of diabetes comes with a recommendation to follow a low-carb diet but the ketogenic diets’ carb requirements are quite low. 

A diabetic that is insulin-dependent must be very careful to adjust the insulin as well as monitor any medication.

Health professionals such as medical doctors and registered dietitians can help with monitoring. 

An event of low blood sugar may need to be treated, and those with diabetes carry a glucagon emergency kit, in the event of a hypoglycemic event the glucagon injection must be administered in order to raise the blood sugar (4).

2. Hepatic Steatosis

Also known as fatty liver disease, is a condition where fat accumulates in the liver in excess amounts. 

There are two types, non-alcoholic fatty liver disease (NAFL), in this case, you may not have liver damage but you may have pain from the liver becoming enlarged. 

Non-alcoholic steatohepatitis (NASH) may have inflammation and in turn, result in liver damage (8).

Because the ketogenic diet has a higher percentage of fat in the diet, some even say there is no limit to the fat you can consume. 

You may have the risk factor of developing this condition.

A good way to help yourself from developing this condition is by avoiding red meat and choosing plant-based fats. 

Fats that are healthier such as vegetable oils, olive oil, avocado oil, fats from fish and poultry.

3. Hypoproteinemia

Abnormally low protein in the blood can result from limiting protein in the diet. 

Also, it can result from liver disease that decreases the making of protein plasma in the liver (9).

Although the keto diet requires a moderate intake of protein, there is a possibility that you may become undernourished with protein. 

Also if you develop hepatic steatosis the damaged liver may impair the production of protein. But to know exactly what causes hypoproteinemia is not quite known. 

4. Kidney stones

Kidney stones form in the kidneys and are usually able to pass without a problem in your urine. 

The problem arises when the stone is larger than 5 millimeters, it can block your ureter. 

This can result in severe back discomfort, abdominal pain, vomiting, or pain when you urinate (2).

Kidney stones can develop from a high intake of animal protein and dehydration. 

Animal protein creates acid an amount that increases the clearing of calcium and uric acid which promotes the forming of kidney stones (7).

A reduction of red meat and other animal proteins can reduce the risk factor of developing kidney stones, but it could lead to an even higher imbalance in macronutrient intake. 

As a side note, those that have kidney disease should consult with their doctor and make sure that the kidney disease is well monitored and not affected by the amount of protein in the diet. 

5. Vitamin and Mineral deficiencies

Micronutrients also known as vitamins and minerals are needed in trace amounts from a variety of foods. 

These micronutrients are important in the maintenance of tissue function, motor, and cognitive development, healthy eyesight, immune system functions, strong bones, resist infectious diseases (1).

Decreasing carbohydrate intake in your diet means that you eliminate refined sugars and processed foods, which is a good thing. 

But you also eliminate fresh fruits and vegetables that are rich in carbs in order to comply with the strict low-carb component of the diet. 

This can result in nutrient deficiencies and you can miss out on a variety of healthy foods that provide a balanced intake of vitamins and minerals (10).

Remember that carbohydrates are not just in breads and grains, they are also found in fruits and starchy vegetables that are often also restricted. 

A single fruit, such as a banana (22 grams) can account for a large portion of the allotted carbs for a day. 

With the keto diet, you risk removing healthy foods that may provide essential micronutrients.

6. Dehydration

As your body creates ketones, the higher the level of ketones the more that needs to be excreted through the urine. 

This may cause dehydration and imbalance of electrolytes such as potassium and sodium.

Also, it is noted that with the keto diet people experience rapid weight loss. Yet the first few pounds that are lost are water weight, followed by fat loss (6). 

This loss of water can lead to dehydration and be mistaken for fat loss. 

Therefore, it is imperative that you drink plenty of water to avoid dehydration and constipation.

7. Keto Flu

Lastly, the famous “keto flu”. 

During the first days or weeks of starting the ketogenic diet, it has been reported by dieters in forums, blogs, support groups, and social media, that a group of symptoms are experienced.

The keto flu presents with symptoms of nausea, vomiting, headaches, tiredness, dizziness, inability to sleep, fatigue, low tolerance in exercising, mood swings, and constipation.

These symptoms can be related to the very low-carb diet. 

Usually, low blood sugar causes these symptoms in an average person that simply has not eaten well throughout the day.

At this point, this is not a medically recognized condition and is more anecdotal evidence that subsides over several weeks or months. 

Yet it makes you wonder how good can keto be for you, shouldn’t eating healthy make you feel good and not bad?

Final Take on Potential Side Effects of Keto

These effects mentioned above are what may possibly happen based on the knowledge of the physiology of the body, yet we still need more studies on the long-term use of this diet.

As a Registered Dietitian, I have often been asked if the keto diet is healthy. 

I tend to err on the side of caution and avoid prescribing restrictive diets unless there is a medical condition that requires it. 

But I do ask, Can you sustain this diet for a prolonged time? 

Do you feel good while on this diet? Do you feel social isolation because of this diet? 

These questions are important to help with reflection when choosing restrictive diets.

With any diet that requires the level of work that it takes to follow the keto diet. I say it may do the work temporarily and quickly. 

But we just don’t know in the long term its effects on the body. 

We know the processes that happen in the body. And can deduce what can happen, but we just don’t know how severely it can affect the body.

The best thing for the body is to feed it with whole grains, legumes, fresh fruit, and vegetables like broccoli, avocado, cauliflower, coconut, starchy vegetables, water intake, and just heart-healthy sources of foods. 

A diet in moderation, will usually not have negative effects on the body.

Always take your current medical conditions into consideration before delving into diet trends that may alter your health, in the short or long term. 

You may consult your doctor in conjunction with a clinical dietitian or registered dietitian in private practice that specializes in monitoring the ketogenic diet.

It is a diet that when prescribed, assessed, and monitored by professionals can give positive results in the short term.

  1. CDC. Micronutrient Facts. 3 Dec. 2020,
  2. Choi, Ji Na, et al. “Renal Stone Associated with the Ketogenic Diet in a 5-Year Old Girl with Intractable Epilepsy.” Yonsei Medical Journal, vol. 51, no. 3, May 2010, pp. 457–59.
  3. Freeman, J. M., et al. “The Epilepsy Diet Treatment: An Introduction to the Ketogenic Diet.” The Epilepsy Diet Treatment: An Introduction to the Ketogenic Diet., Demos Vermande, 1996.
  4. Low Blood Glucose (Hypoglycemia). Accessed 29 May 2021.
  5. Martin‐McGill, Kirsty J., et al. “Ketogenic Diets for Drug‐resistant Epilepsy.” Cochrane Database of Systematic Reviews , no. 11, John Wiley & Sons, Ltd, 2018, doi:10.1002/14651858.CD001903.pub4.
  6. Masood, Wajeed, et al. “Ketogenic Diet.” StatPearls, StatPearls Publishing, 2020.
  7. Negri, Armando L., et al. “[Diet in the treatment of renal lithiasis. Pathophysiological basis].” Medicina, vol. 73, no. 3, 2013, pp. 267–71.
  8. Nonalcoholic Fatty Liver Disease & NASH. Accessed 29 May 2021.
  9. Semrad, Carol E. “142 – Approach to the Patient with Diarrhea and Malabsorption.” Goldman’s Cecil Medicine (Twenty Fourth Edition), edited by Lee Goldman and Andrew I. Schafer, W.B. Saunders, 2012, pp. 895–913.
  10. Shenkin, A. “Micronutrients in Health and Disease.” Postgraduate Medical Journal, vol. 82, no. 971, Sept. 2006, pp. 559–67.
  11. Wheless, James W. “History of the Ketogenic Diet.” Epilepsia, vol. 49 Suppl 8, Nov. 2008, pp. 3–5.