Important but non-specific signs are shakiness, pale skin and seizures. Suspected diagnosis rests on non-specific symptoms: increased glucose consumption, measurable insulin concentration in hypoglycemia, reaction to giving glucagon as well as absence of fatty acid breakdown.
The absolute level of insulin in the blood is less useful here than is glucose consumption, since in children with focal (= localized) forms of CHI normal insulin concentrations can be found just a few centimeters distant from the affected pancreas location. This apparent contradiction finds its explanation in the fact that the liver´s insulin levels regulate the release of glucose from its most important store - liver glycogen. Nevertheless, insulin levels are also important when blood glucose is determined simultaneously.
The increase in blood glucose after administering glucagon is an important criterion.
Hyperinsulinism is unlikely if this reaction is absent and so it is necessary to eliminate other causes. Especially growth disruptions during gestation (small for gestational age, or SGA) or premature birth with pronounced energy consumption are frequent causes of hypoglycemia at neonatal ages. Important hormonal causes are lack of the adrenal hormones cortisol and adrenalin as well as of growth hormone. Also, disruptions in the breakdown of fatty acids and amino acids can cause hypoglycemias.