Treatment of methylmalonic acidemia is effective with dietary therapy, which should begin as early as possible to limit protein intake and reduce intake of methylmalonic acid precursor amino acids; L-carnitine and oral antibiotics may be effective. In some cases, vitamin B12 supplementation in high doses is effective, and in vitamin B12-dependent methylmalonic acidemia, vitamin B12 may be given first, 1-5 mg/d for 1 week. If an effect occurs, maintenance doses can be given over time, usually at a dose of 1 mg per week, adjusted according to clinical and biochemical response. Methylmalonic acidemia, also known as methylmalonic aciduria, is autosomal recessive, and the main clinical manifestations are early infantile onset, severe intermittent ketoacidosis, and increased methylmalonic acid in the blood and urine, often accompanied by central nervous system symptoms.