No, vitamin B12 deficiency alone is typically not a cause for concern over cancer. Most cases are caused by diet, aging or problems with the way the body absorbs B12. But if you’re experiencing symptoms… 

Low levels of vitamin B12 can leave you feeling tired, weak and less energetic than normal. Low B12 can also cause dizziness, pale skin, memory issues and tingling or numbness in the hands and feet.… 

Tiredness and fatigue are early signs of vitamin B12 deficiency. Weakness and low energy are also common. You may also experience pale skin, dizziness, or shortness of breath during normal activities. As the deficit worsens… 

Low vitamin B12 is not usually a sign of cancer—it most commonly happens due to poor diet, low stomach acid, or absorption problems.