Vitamin B₁₂ deficiency can be manifested as dizziness and fatigue, optic nerve damage, psychiatric disorders, anemia and so on. If the above symptoms occur, also can not judge by themselves as a lack of vitamin B₁₂, the specific lack of vitamin B₁₂ need to go to the hospital for examination, under the guidance of the doctor or pharmacist for treatment, do not self-medication, in order to avoid adverse reactions. 1. Dizziness and fatigue: Vitamin B₁₂ deficiency will cause dizziness, dizziness and dullness of the mind, and fatigue and loss of appetite even after more than 8 hours of sleep. 2. Optic nerve damage: long-term lack of vitamin B₁₂ will affect vision, and in severe cases, optic nerve damage may occur, which can cause blurred vision. 3. Mental illness: Studies have found that vitamin B₁₂ deficiency can lead to depression and other mental illnesses. 4. Anemia: Vitamin B₁₂ deficiency can also lead to anemia and slow reaction time.