Objectives: To investigate the diagnostic value of accessible fingertip mean corpuscular volume (MCV) combined with a visible “beefy red” patch in the diagnosis of vitamin B12 (VB12) deficiency in local clinics and hospitals without in-house clinical laboratories, especially in remote areas.Materials and methods The medical history data of patients complaining of oral mucosal pain at the Stomatological Hospital of Southern Medical University were reviewed. All included patients underwent fingertip blood routine examination, specific serological test (serum VB12, folic acid, iron, and ferritin), and detailed oral clinical examinations. According to the results of the serum VB12 test patients were divided into case and control groups. The diagnostic value of the “beefy red” patch and elevated MCV in VB12 deficiency was evaluated by the receiver operator characteristic curve.Results There are more female patients in the case group (n=81) and the control group (n=60). Compared to the control group, the number of patients with “beefy red” patch and abnormal MCV increased significantly in the case group (P<0.05). The diagnostic test, “beefy red patch” has high sensitivity but low specificity, “MCV>100 fL” has high sensitivity but low specificity, and “MCV>100 fL combined with beefy red patch” has maximal specificity, and area under the curve.Conclusions Visible oral “beefy red” patch combined with accessible fingertip blood MCV could improve the rate of diagnosis in VB12 deficiency, especially in the elderly in local clinics and hospitals without in-house clinical laboratories in China, which is conducive to early disease detection and treatment.