Explaining medical ketogenic diets
Ketogenic diets are very high in fat, provide adequate protein and are very low in carbohydrate. They mimic the state of starvation, encouraging the body to produce ketones, which become an energy source for the brain.
Ketogenic diets may be used to help manage specific medical conditions. For example, as a non-pharmacological treatment for epilepsies in children, young people and adults if seizures are not controlled with anti-seizure medications.
Patients are provided with an individualised diet prescription by a specialist team, including a dietician. Allowances vary depending on the type of ketogenic diet chosen, the patients age, weight, growth, activity levels, medical conditions, and other factors.
Carbohydrate restrictions
The recommended carbohydrate intake for patients on ketogenic diets vary. For example, carbohydrate may be restricted to 10 to 20g per day in children on ketogenic diets. To put this in context, the UK government recommends a carbohydrate intake between 134g to 333g per day in children aged 1 to 18.
Patients on a medical ketogenic diet need to weigh all food and drink to ensure they adhere to the carbohydrate restrictions set out in their dietary prescription.
Carbohydrate exposure from non-food sources, such as medicines, requires consideration and should be limited where possible. Dietary restrictions should be adjusted to account for carbohydrate consumption through medicine use.
Carbohydrates in medicines
Carbohydrates (sugars) could come from the active ingredient (drug) itself or more commonly from excipients used in medicines. Liquid medicines specifically can be an unrecognised source of carbohydrate.
When prescribing or reviewing medication for a patient on a medical ketogenic diet first consider whether the medicine contains carbohydrates (or a source of carbohydrates); avoid where possible or limit exposure.
Excipients to avoid
The following excipients should generally be avoided where possible in patients on a medical ketogenic diet. This is because they are either a carbohydrate or a source of carbohydrate.
This list of excipients is not exhaustive.
Suitable excipients
The following excipients are generally considered safe for those on medical ketogenic diets. However, avoid large amounts of non-carbohydrate sweeteners as they can sometimes cause stomach upset and may encourage a sweet tooth.
This list of excipients is not exhaustive.
Determining the carbohydrate content
There is no single resource available listing the quantities of carbohydrate present in medicines.
Use the Summary of Product Characteristics (SPC) for a medicine and the excipient lists above to identify if a medicine contains carbohydrate (or a source of carbohydrates). Select medicines/formulations which are carbohydrate free where possible. When this is not possible, consider the amount of carbohydrate in a medicine and explore alternative medicines/formulation to limit carbohydrate burden. Excipients may vary between different manufacturers, brands and formulations.
If present, contact the manufacturer(s) to confirm specific carbohydrate content of each of the medicine(s). Ask for this information in milligrams or grams.
Collate the following information before contacting the manufacturer:
- name [and brand if relevant] of medicine
- strength of medicine
- formulation of medicine
- a batch number and expiry date- useful as formulations can change
Be aware the manufacturer may not be able to provide information straight away, so factor this in as part of the process. If the medicine is essential, for example, antibiotics, it may need to be started before the carbohydrate content is known. Consider the pharmaceutical principles below for hints and tips to minimise carbohydrate content.
Using this information in practice
Once you have received the information relating to carbohydrate content from the manufacturer, consider calculating carbohydrate content for each medicine (consider the prescribed dose and frequency) and total daily exposure from all medicines.
Where there are multiple options, choose the brand/formulation with the lowest total daily carbohydrate exposure.
This information can be shared with the specialist dietician who will assess impact and adjust dietary intake from food sources.
Pharmaceutical principles
Healthcare professionals should consider the following when choosing formulations of medicines for people on a medical ketogenic diet:
- tablets and capsules usually contain less carbohydrate than oral suspensions and solutions and are often the preferred formulation
- suppositories can be used since any carbohydrate they contain is not absorbed
- syrups, elixirs and chewable tablets should be avoided, or use minimised because they often contain carbohydrate-based sweeteners/agents
- sugar-free preparations aren’t necessarily carbohydrate free, for example, sorbitol is a source of carbohydrate
- avoid large amounts of sweeteners as they can sometimes cause stomach upset and may encourage a sweet tooth
- when treating constipation, avoid lactulose as a precautionary measure as carbohydrate load is high (though there is no evidence that it is absorbed)
- if a patient requires IV fluids use sodium chloride over glucose if clinically appropriate
Further information
If switching a patient from liquid medications to a solid dosage form then see our guidance on considerations when switching between solid doses and liquids
Detailed information on medical ketogenic diets is available from a variety of resources. Examples include: