Ketogenic diets

Ketogenic diets are a very high fat, very low carbohydrate, moderate protein diet that have been used since the 1920s to treat epilepsy. 

The diets are a medical treatment, and are usually only considered when at least two suitable medications have been tried and not worked. Ketogenic diets are an established treatment option for children with hard to control epilepsy. However, adults may also benefit from ketogenic diets. 

Dietary treatments for epilepsy must only be followed with the support of an experienced epilepsy specialist and dietitian (food specialist).

Usually the body uses glucose (a form of sugar) from carbohydrates, found in foods like sugar, bread or pasta, for its energy source. Chemicals called ketones are made when the body uses fat for energy - this is called ketosis. With ketogenic diets, the body mostly uses ketones instead of glucose for its energy source. 

It is not clear exactly how the diets help reduce seizures in some people. Research has shown that a particular fatty acid called decanoic acid, may be involved in the way the diets work. 
 

The diets may not work for everyone but are suitable for many different seizure types and epilepsy syndromes. If you, or your child, has a condition where a high fat diet would cause problems, the diets may not be suitable. 

Ketogenic diets can be adapted to diets from all different cultures, as well as for people with allergies or those on modified texture diets. The dietitian will calculate the diet and try to include foods you or your child likes. The diets can be used in children and adults of any age, although infants need close monitoring.

There are different forms of the ketogenic diet. The types of foods eaten and how each diet is calculated are slightly different, but all forms have shown effectiveness, in randomised controlled trials, in reducing seizures for some people.

To make sure the diets are nutritionally balanced, an experienced dietitian works out exactly how much of which foods the person can eat each day. To help with this, people have individual recipes, are given support on how to plan meals, and are guided on which foods should be avoided. As the diets can be quite restrictive, the dietitian will recommend any vitamin and mineral supplements that are needed.

Regular follow-ups with the dietitian, and medical team, will monitor your or your child’s growth (height and weight, if applicable), health, epilepsy, and if there is a need for any change to anti-seizure medication (ASM), such as changing to sugar-free versions. If the diet is followed carefully, individuals do not put on weight, or lose weight inappropriately.

You may be given a diary to record the number and type of seizures you or your child has while on the diet. As food can affect how we feel or act, you may be asked to note any changes in your or your child’s mood, alertness and overall behaviour. It usually takes at least three months to see whether the diet is effective. 

The length of time the diet is followed may vary, but if an individual remains seizure-free, has fewer seizures, or maintains other benefits, such as improved quality of life, they may consider (with their medical team) slowly coming off the diet after two years.

To check that the diet is producing ketones, ketone levels are checked using a blood test, or a urine analysis stick, which is dipped into a container of your or your child’s urine. The blood test involves a small pin prick on the finger (similar to monitoring diabetes). You can decide with your doctor, and dietitian, which method to use.

Constipation is common, partly due to a lack of fibre. This can easily be treated. Hunger, vomiting and lack of energy are also common at the start of treatment, but these tend to decrease with time and may be avoided with careful monitoring. Many people report an increase in energy and feeling more alert once they are used to the diet.

A clinical trial at Great Ormond Street Hospital in 2008 showed that around 4 in 10 children (38%) who started a ketogenic diet had reduced seizures and were able to reduce their anti-seizure medication. Although not all children had better seizure control, some had other benefits such as increased alertness, awareness, and responsiveness. This was the first trial of the 
ketogenic diet for children with epilepsy. There are now other high-quality trials showing the diet to be effective in infants and adults with epilepsy. 

You can discuss the option of starting the diet with your GP or paediatrician/neurologist.

K.Vita® is a supplement made from MCT fats, designed as an alternative treatment to the ketogenic diet for children and adults with epilepsy. It is taken alongside a ‘healthy’ diet, and is not restricted in carbohydrates, although some ketogenic centres also use it as part of a ketogenic diet. Your neurologist can request a prescription for K.Vita® from your GP.

• Great Ormond Street Hospital (GOSH) - enter ‘ketogenic diet’ into the search box.
• Matthew’s Friends - Information and support for patients and families considering the ketogenic diet.
• The Daisy Garland - Provides help and support for families and funding for ketogenic dietitians.

Epilepsy Society is grateful to Dr Natasha Schoeler, Senior Research Fellow and Specialist Paediatric Dietitian, UCL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital for Children, who reviewed this information.

Information produced: June 2026. Review date: June 2028.