My 16 mo old has been diagnosis with ketonic hypoglycaemia with no known cause yet. c-peptide levels came today and are high but insulin levels not. causes?

Metabolic disorder: Metabolic disorders like this sounds are very difficult to diagnose and get exact resons for. Many times the reason won't show up on routine blood work, and you need to do things like biopsies of muslcle, etc, to pin down the cause. Sounds like a possible mitochondrial disorder where she can't metabolize her glucose correctly, but other possibilities also exist. Get to a metabolic specialist!

Doesn't make sense: Elevation in c-peptide with low Insulin doesn't make sense. Ketosis can only happen when Insulin levels are low, though many causes for ketotic hypoglycemia. Most often we see this in the toddler who's been sick and hasn't been eating well. Since Insulin levels were measured, i assume that gh, cortisol were normal. Glycogen storage disease and defects in gluconeogenesis far less common.