Vitamin B12, also known as cobalamin, is absorbed by the body and metabolized in the liver. The symptoms of vitamin B12 deficiency in men and women are basically the same, but due to the different degrees of deficiency, the symptoms that appear in the body will be different. Local symptoms: 1. Eye symptoms: vitamin B12 has the function of promoting eye metabolism, and a small amount of deficiency can compensate for and does not affect this function, but a large amount of deficiency will lead to blocked eye metabolism and symptoms such as eye edema and painless vision loss; 2. parts, palms, soles, nail parts, and may also have hair showing grayish white. Systemic symptoms: 1. Nervous system: Vitamin B12 is an important substance to ensure the renewal of myelin in the nervous system, a small amount of vitamin B12 deficiency, the renewal of myelin is only slightly damaged, some people will have symptoms such as memory loss and numbness of both lower limbs. In case of severe deficiency, some people may experience symptoms such as mental depression, tremors of the limbs, neurological disorders, and even diffuse neural demyelination lesions; 2. Blood system: one of the main functions of vitamin B12 is to participate in hematopoiesis of the body, and severe deficiency of vitamin B12 will affect hematopoiesis, and some people may experience symptoms such as anemia, fever, weakness, megaloblastic anemia, 3, digestive system: vitamin B12 can promote the absorption of some nutrients, if a large amount of vitamin B12 deficiency, it will lead to the absorption of some nutrients is blocked, thus appearing abdominal pain, bloating, diarrhea and other gastrointestinal symptoms; 4, endocrine system: lack of more vitamin B12, may appear endocrine disorders, some men will show hair loss, acne situation. In addition, there can be loss of appetite, gum bleeding and other performance, the above symptoms are more common in men with vitamin B12 deficiency, vitamin B12 may be caused by insufficient intake or excessive loss. If any of these abnormalities occur, you should seek medical attention to identify the cause of the deficiency, actively supplement vitamin B12 and treat the symptoms.