Abstract
<jats:p>A 59-year-old male was diagnosed with mild macrocytic anemia during a health examination, without any specific complaints. Complete blood count revealed macrocytic anisocytosis, and microscopic examination showed red blood cell size variation and neutrophilic hypersegmentation. Follow-up complete blood count and blood smear microscopy, combined with complete biochemical panel (elevated bilirubin, lactate dehydrogenase, and homocysteine) and anemia panel (decreased vitamin B12, normal folate and ferritin), confirmed the diagnosis of vitamin B12 deficiency megaloblastic anemia based on the diagnostic criteria for megaloblastic anemia. Targeted vitamin B12 supplementation was administered to correct hematopoietic substrate deficiency and correct cellular DNA synthesis disorders. After standardized treatment, the patient's hematopoietic function gradually recovered, with complete blood count, biochemical, and anemia panel indicators all returning to normal. No anemia-related neurological or digestive symptoms were observed, and the clinical outcome was favorable.</jats:p>