Le ketogenic diet is a low-carb, high-fat diet commonly used for weight loss.

Restricting carbohydrates and increasing fat intake can lead to ketosis, a metabolic state in which your body relies primarily on fat for energy instead of carbohydrates ().

However, the diet also comes with risks that you should be aware of.

Here are 7 dangers of the ketogenic diet to be aware of.

1. Can lead to keto flu

Carb intake on the keto diet is generally limited to less than 50 grams per day, which can be a shock to your body ().

As your body depletes its carbohydrate stores and shifts to using ketones and fats for fuel at the start of this diet, you may experience flu-like symptoms.

These include headaches, dizziness, fatigue, nausea and constipation – due in part to dehydration and which occur as your body adapts to ketosis ().

While most people who experience the problem feel better within a few weeks, it is important to monitor these symptoms throughout their diet, stay hydrated, and eat foods rich in sodium, potassium, and other electrolytes ().

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As your body adapts to using ketones and fats as its primary energy source, you may experience flu-like symptoms when starting the keto diet.

2. Can Stress Your Kidneys

High-fat animal foods, like eggs, meat, and cheese, are staples of the keto diet because they contain no carbs. If you eat a lot of these foods, you may have a higher risk.

This is because high consumption of animal foods can make your blood and urine more acidic, leading to increased excretion of calcium in your urine (, ).

Some studies also suggest that the keto diet reduces the amount of citrate released in your urine. Since citrate can bind to calcium and prevent kidney stones from forming, reduced levels of it may also increase your risk of developing them ().

Additionally, people with chronic kidney disease (CKD) should avoid keto, as weakened kidneys may be unable to remove the acid buildup in your blood that results from these animal foods. This can lead to a state of acidosis, which can worsen the progression of CKD.

Additionally, they are often recommended for people with CKD, while the keto diet is moderate to high in protein ().

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Eating a lot of animal foods on the keto diet can lead to more acidic urine and a higher risk of kidney stones. This acidic state can also worsen the progression of chronic kidney disease.

3. May Cause Digestive Problems and Changes in Gut Bacteria

Since the keto diet limits carbs, it can be difficult to meet your daily fiber needs.

Some of the richest sources of fiber, such as high-carb fruits, starchy vegetables, whole grains and beans, are eliminated from the diet because they provide too many carbohydrates.

As a result, the keto diet can lead to digestive discomfort and constipation.

A 10-year study of children with epilepsy on a ketogenic diet found that 65% of children reported a common side effect ().

Plus, fiber feeds the beneficial bacteria in your gut. Having a healthy gut can help boost immunity, improve mental health and reduce inflammation ().

A low-carb diet that lacks fiber, like keto, can have a negative effect on your health – although current research on this topic is mixed ().

Some fiber-rich keto foods include flax seeds, chia seeds, coconut, broccoli, cauliflower, and leafy greens.

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Due to its carbohydrate restrictions, the keto diet is often low in fiber. This can trigger constipation and negative effects on gut health.

4. Can Lead to Nutrient Deficiencies

Because the keto diet restricts several foods, particularly nutrient-dense fruits, whole grains, and legumes, it may not provide recommended amounts of vitamins and minerals.

In particular, some studies suggest that the keto diet does not provide enough calcium, vitamin D, magnesium, and phosphorus ().

A study that evaluated the nutritional composition of common diets found that very low-carb eating habits, similar to keto, provided sufficient amounts of only 12 of the 27 vitamins and minerals your body needs to get from food. ().

Over time, this can lead to.

Notably, guidelines for clinicians managing people on a very low-calorie keto diet for weight loss recommend supplementing with potassium, sodium, magnesium, calcium, omega-3 fatty acids, psyllium fiber and vitamins B, C and E ().

Keep in mind that the nutritional adequacy of this diet depends on the specific foods you eat. A diet rich in healthy, low-carb foods, such as avocados, nuts, and non-starchy vegetables, provides more nutrients than processed meats and keto treats.

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Some studies suggest that keto provides insufficient vitamins and minerals, including potassium and magnesium. Over time, this could lead to nutrient deficiencies.

5. May cause dangerously low blood sugar

Low-carb diets like keto have been shown to help manage blood sugar levels in people with diabetes.

In particular, some studies suggest that keto may help reduce levels of hemoglobin A1c, a measure of average blood sugar (, , ).

However, people with type 1 diabetes may be at high risk of episodes of low blood sugar (hypoglycemia), which is characterized by confusion, shaking, and sweating. Hypoglycemia can lead to coma and death if left untreated.

A study of 11 adults with type 1 diabetes who followed a ketogenic diet for more than 2 years found that the median number of hypoglycemia events was close to 1 per day ().

People with type 1 diabetes usually experience hypoglycemia if they take too much insulin and don't eat enough carbohydrates. So, a low-carb keto diet may increase the risk.

Theoretically, this could also happen to people who take insulin medications.

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Although low-carb diets have been shown to improve blood sugar control in people with diabetes, they may also increase the risk of hypoglycemia, especially if you have type 1 diabetes.

6. May harm bone health

The keto diet is also associated with impairment.

Several animal studies link the keto diet to decreased bone strength, likely due to losses in bone mineral density, which can occur as your body adapts to ketosis (, ).

In fact, a 6-month study of 29 children with epilepsy on the keto diet found that 68% had a lower bone mineral density score after following the diet ().

Another study of 30 elite walkers determined that those who followed keto for 3,5 weeks had significantly higher levels of blood markers for bone breakdown, compared to those who dieted ().

Nevertheless, further research is warranted.

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The keto diet may lower your bone mineral density and trigger bone breakdown over time, although more study is needed.

7. May increase your risk of chronic diseases and premature death

The effect of the ketogenic diet on your risk of chronic disease, such as heart disease or cancer, is hotly debated and not fully understood.

Some evidence suggests that high-fat, low-carb diets that focus on animal foods may lead to poor health outcomes, while diets that emphasize the benefits (, ).

A long-term observational study of more than 130000 adults linked diets low in animal-based carbohydrates to higher rates of death from heart disease and all causes ().

In contrast, low-carb, vegetable-based diets were associated with a lower rate of death from heart disease and all causes ().

Another study of more than 15000 adults found similar results, but linked low- and high-carb diets to a higher all-cause mortality rate, compared to moderate-carb diets in which carbohydrates accounted for 50 to 55% of total daily calories ().

However, more substantial studies are needed.

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Although research is mixed, some evidence suggests that low-carb diets focused on animal foods may lead to higher mortality rates from heart disease, cancer, and all causes.

The bottom line

Although the keto diet is linked to weight loss and in the short term, it can lead to nutrient deficiencies, digestive issues, poor bone health, and other problems over time.

Because of these risks, people with kidney disease, diabetes, heart or bone disease, or other health problems should talk to their healthcare provider before trying the keto diet.

You can also consult a dietitian to plan and monitor your nutrient levels during this diet to minimize the risk of complications and nutrient deficiencies.