Keto diet side effects include dehydration, diarrhea, and nutrient deficiencies. The shift to burning fat instead of sugar, also known as ketosis, triggers side effects.

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A keto diet can cause individuals to lose water before losing fat. As a result, you may have dehydration, which is when your body loses too much fluid.

Symptoms of dehydration include:

Common side effects of a keto diet are gastrointestinal (GI) symptoms like:

Of those problems, diarrhea happens more frequently, This may be due to difficulty absorbing the high-fat content of the diet.

The keto diet could lead to kidney stones. These are mineral deposits that can develop in your kidneys.

Kidney stones are more likely to occur in people without kidney disease following keto due to the increase in animal-based and high-fat foods. For those with kidney disease, keto can lead to further long-term kidney damage.

Ketosis can trigger ketoacidosis in individuals with type 1 diabetes. The condition can be fatal if left untreated.

Ketoacidosis may be responsible for kidney stone formation due to decreased citrate and pH levels and increased calcium levels in the urine.

Athletes may find the keto diet helpful for weight loss and improved sports performance. However, it may decrease performance on high-intensity cycling and running tasks compared to a high-carb diet.

For some people, going on the keto diet can lead to the keto flu, which can cause symptoms like:

Constipation
Dizziness
Exercise tolerance difficulties
Fatigue
Headache
Insomnia
Nausea or vomiting

You can minimize the effects of keto flu by drinking plenty of water and increasing electrolyte intake. Slowly decreasing your carb intake can help also.

Many fruits and vegetables may be limited or eliminated on the keto diet to keep carb intake low.

This may lead to a lower intake of important nutrients, such as:

CalciumFiberIronMagnesiumPotassiumVarious vitamins

Specifically, you may miss out on folate and thiamin as well as vitamins A, B6, B12, C, E, and K. All essential for many bodily functions and development.

Due to the keto diet’s strict restrictions, people may regain any lost weight when they return to typical eating patterns. Keto is hard to follow long-term.

Recommendations for the length of time to stay on the diet range from 2-3 weeks up to 12 months.

While the keto diet has some undesirable side effects, you could experience benefits for your physical and mental health.

Weight Loss

The keto diet can be helpful for weight loss. The initial weight loss is water weight. However, after this, you may begin to lose fat. You may eat fewer calories because following the keto diet may make you feel less hungry.

Blood-Related Changes

During the initial 6-12 months of the diet, people may have blood pressure, blood sugar, and triglyceride decreases. They might also see an increase in high-density lipoprotein (HDL) cholesterol.

Emotional and Cognitive Changes

The keto diet may be helpful for some specific mental health and cognitive conditions. It may improve:

Anxiety
Auditory and visual hallucinations
General mood in people with bipolar disorder

More studies are needed.

Decrease in Seizure Frequency

Keto diets have been used for over 100 years for epilepsy treatment. They are effective in decreasing seizure frequency in people with drug-resistant epilepsy.

Individuals with the following conditions should avoid the keto diet:

Eating disorders or a history of eating disordersFat metabolism disorders (disorders of fat storage)Gallbladder diseaseLiver failure or other liver conditionsPancreatitisThyroid problems, like hypothyroidism

If you’ve been diagnosed with diabetes and prescribed insulin or hypoglycemic medications, talk with a doctor before starting this diet. You might have severe hypoglycemia without medication adjustments beforehand.

Following a keto diet can be good for some people. Though the diet emphasizes high-fat and low-carb foods, it allows for moderate-protein.

This eating approach can be helpful for people with dementia or epilepsy and those who are overweight or have obesity.

Following the keto diet can be bad for you due to its high-fat content. Low-density lipoprotein (LDL) cholesterol levels increase when you eat more saturated fats like beef, pork, cheese, and butter. Higher LDL cholesterol levels increase the risk of heart disease or stroke.