A 3-year-old boy from rural Maharashtra presents with recurrent episodes of severe hypoglycemia, hepatomegaly, and lactic acidosis. Serum lactate is 8 mM (normal <2), and blood glucose is 35 mg/dL despite fasting for only 2 hours. Genetic testing confirms homozygous loss-of-function mutation in the LDHA gene (lactate dehydrogenase A). What is the most appropriate immediate next step in management?