It is well known that dehydration is a potential adverse effect of a ketogenic diet, which is one higher in fat with adequate protein and lower in carbohydrates.
Nutritionists should be watchful, in particular, of those who use ketogenic diets as therapy for certain conditions such as epilepsy and type 2 diabetes.
A study in epileptic children on ketogenic diets, for example, found dehydration to be the "most common early-onset compllication"and higher in those who fasted (1-2). The dehydration could be partly blamed on the incidence of GI tract adverse effects (1).
When treating those with type 2 diabetes with a ketogenic diet, it is advisable to instruct drinking up to eight 8 oz. glasses of water daily. There may also be need for adjusting those recommendations if certain medications were used such as diuretics.
According to the researchers who performed an intervention trial on those with type 2 diabetes and a ketogenic diet that resulted in a few adverse effects, the following was concluded: "Until we learn more about using low carbohydrate diets, medical monitoring for hypoglycemia, dehydration, and electrolyte abnormalities is imperative in patients taking diabetes or diuretic medications" (1).
The lower carbs can have a diuretic effect on the body, which should lead clinicians to be aware and make recommendations for increased water intake as necessary.
1. Duschowny MS. Food for thought: The ketogenic diet and adverse effects in children. Epilepsy Curr. 2005 July;5(4):152-154. Available at: Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1198735/?tool=pmcentrez
2. Kang HC, Chung da E, Kim DW, Kim HD. Epilepsia 2004;45:1116-1123. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1198735/?tool=pmcentrez