Side-effects of the Ketogenic Diet

When a child starts on the Ketogenic Diet, they may feel lethargic and lack energy for several weeks.

During the initiation period on the diet, they may also experience the following easily treatable, but potentially serious side-effects:

  • Dehydration
  • Hypoglycaemia (low blood sugar levels) - even without fasting
  • Low-grade acidosis (increased blood acidity)
  • Constipation
  • Hunger
  • Diarrhoea
  • Vomiting
  • Abdominal pain
  • Changes in taste

If your child remains on the diet over a longer period of time, as with any medical therapy, they may experience complications. Some of the documented side-effects of being on the Ketogenic Diet over the longer-term include:

  • Kidney stones
  • Constipation
  • Dehydration
  • High blood cholesterol and triglyceride levels
  • Slowed growth or weight gain
  • Bone fractures
  • Vitamin deficiencies (e.g. selenium, vitamin D, zinc etc.)

Typically, children come off the Ketogenic Diet after around two years.1  The treating Neurologist will determine when the diet will be discontinued and the method for gradual discontinuation.


  • 1Martinez, C. C., Pyzik, P. L. and Kossoff, E. H. (2007), Discontinuing the Ketogenic Diet in Seizure-Free Children: Recurrence and Risk Factors. Epilepsia, 48: 187–190. doi: 10.1111/j.1528-1167.2006.00911.x