VLCAD is a treatable disorder of fatty acid metabolism caused by an inability to use very-long-chain fats for energy. Fatty acid metabolism occurs during prolonged fasting and/or periods of increased energy demands (fever, stress) when energy production relies increasingly on fat metabolism. Severe VLCAD can cause hypoketotic hypoglycemia, hepatomegaly, cardiomyopathy and arrhythmias, lethargy, and failure to thrive. The age of onset can be from early infancy to adulthood. Infants can present with hypoglycemia, liver disease, and cardiomyopathy, children who present outside of the newborn period present with hypoglycemia, enlarged liver, muscle weakness and most patients who show symptoms in teen years or adulthood have periods of muscle weakness and cramping with reddish-brown urine. Full gene sequencing will identify greater than 98% of mutations in affected individuals. Carrier testing for biological family members is available once mutations are known.