Table 1.

Signs of an IEM

When to consider a glycogenolysis disorder	When to consider a fatty acid oxidation disorder	When to consider a gluconeogenesis disorder
- Fasting hypoglycaemia	- Fasting hypoglycaemia	- Long fasting hypoglycaemia
- Presence of ketosis (except for GSD I)	- Absence of ketosis	- Presence of ketosis
- High blood lactate	- High CPK levels	- Lactic acidosis
- Hyperuricaemia	- Acylcarnitine accumulation (example: MCAD: high C8 and high C8/C2 ratio)	- High alanine level during fasting
- Hypertriglyceridaemia	- Urine organic acid accumulation (example: HMG-CoA lyase: 3-Hydroxy-3-Methylglutaric acid)	- Blood glycerol and urine glycerol-3-phosphate accumulation during fasting
- Hepatomegaly	- High free carnitine plasma level (CPT1)
- Muscular signs	- Family history of sudden death