Recurrent aphthous stomatitis (RAS), is characterized by recurrent, ulcerative oral lesions which are often painful, single or multiple, round or ovoid ulcers, present during childhood or adolescence and recurs for variable periods of time. Discomfort in patients with RAS is relatively high. The patients’ life quality is affected by painfulness of these mucosal lesions.The presence of ulcerations increase the flow of saliva, and interfere with eating, drinking and speaking. Since the etiology of RAS is unknown, many patients are receiving medication only to relieve pain. RAS patients with anemia and lower hemoglobin levels have reduced capacity of the blood to carry oxygen to oral mucosa, finally resulting in atrophy of oral mucosa. Atrophic oral epithelium in hematinic deficient patients may explain why some patients with deficiencies of hematinics are prone to have RAS.The measurements of vitamin B12 metabolites such as MMA and Hcy have been shown to be more sensitive in the diagnosis of vitamin B12 deficiency measurement of serum B12 levels alone which is one of the etiological factor in RAS.