The ketogenic diet is a special diet regimen. Under normal circumstances, a person needs a constant intake of food to provide energy and various nutrients to the body. The supply of energy comes mainly from the three major nutrients in food: carbohydrates (sugars), proteins and fats. Among them, carbohydrates provide about 45% (infants) to 60% (older children) of the total daily energy, generally about 50%. The ketogenic diet is a high-fat, low-carbohydrate dietary regimen that converts the body’s energy supply to a predominantly fat-based diet. In a ketogenic diet, 90% of the body’s daily energy supply comes from fat, with protein and carbohydrate together providing only 10% of the energy supply. Since ketone bodies are produced during fat catabolism, a high-fat diet produces large amounts of ketone bodies in the body, hence the name ketogenic diet. The mechanism of the ketogenic diet for epilepsy is still unknown, but the ketogenic diet has a long history of treating epilepsy. The ketogenic diet actually simulates a metabolic process that occurs in a normal human body during starvation. In ancient times, it was found that certain epileptic patients had fewer seizures when they were starving. In the 1820s, the first ketogenic diet was developed to reduce seizures by changing the proportion of food ingredients in the diet. However, the diet was found to be very tedious to prepare, requiring the patient’s parents or family to be buried in the kitchen daily, weighing, calculating and preparing the food, while seizure control rates were not high. Therefore, with the introduction of early antiepileptic drugs such as luminal and phenytoin sodium, the ketogenic diet regimen was gradually abandoned. This is because the treatment with antiepileptic drugs is not only effective, but also much easier to take. As generations of antiepileptic drugs have been developed and applied to the clinic, decades have passed, yet it has been found that 20-30% of patients with epilepsy still have seizures that are difficult to control. Therefore, in recent years, the ketogenic diet has received renewed attention as a special dietary therapy for the treatment of refractory epilepsy. The ketogenic diet is not the preferred method of antiepileptic treatment for patients with epilepsy, and it is currently used mainly for the treatment of refractory epilepsy. Refractory epilepsy is defined as epilepsy in which two or more first-line antiepileptic drugs have been used in succession and the maximum tolerated dose has been reached, and the treatment has been ineffective for a reasonable period of time. Currently, the ketogenic diet is widely used in various types and causes of refractory epilepsy, such as infantile spasms (IS), Lennox-Gastaut syndrome (LGS), Landau-Kleffner syndrome (LKS), and Ketosis. Kleffner syndrome (LKS), Dravet syndrome, etc. Although the ketogenic diet is now widely used worldwide, there are many retrospective and prospective clinical studies that have concluded that the ketogenic diet responds well in the treatment of refractory epilepsy. However, due to the lack of a globally standardized ketogenic diet treatment protocol, countries such as Europe and the United States are observed with their own formulated diet protocols, making it difficult to evaluate clinical data in general, and the efficacy of the ketogenic diet reported by various research institutions varies. The overall efficiency of the ketogenic diet for seizure control is about 50-70%. In prospective studies of the ketogenic diet for 6 months, the lowest reported efficacy was 50% or more seizure remission in 27% of children and the highest was 90% or more seizure remission in 75% of children, which may be related to the dietary regimen and patient selection criteria. The ketogenic diet alters the normal metabolic processes of the body and may have adverse effects on the body. Common early adverse effects of ketogenic diet are: (1) dehydration (weight loss greater than 5% of basal body weight, urine specific gravity greater than 1.020); (2) gastrointestinal disorders, of which diarrhea is the most common, followed by nausea, vomiting and constipation; (3) infectious diseases, mainly pneumonia, cystitis and non-specific fever; (4) other metabolic disorders, such as hypertriglyceridemia, hypercholesterolemia, high-density lipoprotein (HDL), and cholesterol. (4) other metabolic disorders such as hypertriglyceridemia, hypercholesterolemia, hypoHDL, symptomatic hypoglycemia, hypoproteinemia, hypomagnesemia, hyponatremia, and persistent acidosis; (5) rarely, hepatitis and acute pancreatitis. Long-term adverse effects include reduced bone mineral density, kidney stones, iron deficiency anemia, and secondary carnitine deficiency. Therefore, children should be monitored for liver and kidney function, blood glucose, lipids, and blood ions before the start of ketogenic diet therapy, and blood glucose, lipids, and liver and kidney function should be monitored regularly during the course of treatment. In order to better control seizures, reduce the side effects of the ketogenic diet, and improve the taste of the ketogenic diet and simplify the preparation steps, so that the ketogenic diet can be better clinically applied and more easily accepted by children and parents, the adjustment of the ketogenic diet protocol has been the focus of research in recent years. The long-term intake of large amounts of fat is inevitably accompanied by hyperlipidemia. To reduce the risk of cardiovascular diseases such as atherosclerosis, the ratio of polyunsaturated to saturated fatty acids in the ketogenic diet needs to be increased. Currently, there are three types of ketogenic diets, depending on the fat composition of the ketogenic diet: (1) the classical ketogenic diet, which consists of long chain triglyceride (LCT) and a small amount of protein and carbohydrates, with a ratio of 4:1 or even 6:1 of fat to protein and carbohydrates. (2) A ketogenic diet consisting of medium chain triglyceride (MCT) has a ratio of fat to protein to carbohydrate of 1.5:1. The Atkins diet is a modified form of the classical ketogenic diet, which does not restrict protein and energy intake, with a recommended carbohydrate intake of 10 g/day for children (15 g/day for adults) and a fat to protein to carbohydrate mass ratio of 0.9:1. The classical ketogenic diet is currently the most commonly used treatment protocol. Some researchers divided patients into three groups and gave them the three ketogenic diet regimens, and found that the classical ketogenic diet was the most effective and well-tolerated. Currently, research and adaptation of ketogenic diet regimens are still underway in various countries. In addition to the above-mentioned adjustment of the ratio of various food components in the diet regimen, the main studies include the necessity of the fasting phase before starting the ketogenic diet, the indications and contraindications of the ketogenic diet, the duration of the ketogenic diet, and the effect of the ketogenic diet on the shared antiepileptic drugs. There are no uniform conclusions regarding the above studies. In conclusion, for some refractory epilepsies, the ketogenic diet as a special dietary therapy is a worthy treatment option to try. Although the possibility of the ketogenic diet becoming the preferred treatment option for epilepsy in the future cannot be ruled out with the adjustment and improvement of the dietary regimen, at present, the ketogenic diet is not yet the preferred treatment option for epilepsy, and we still need to pay great attention to its side effects.