A Vitamin B12 Test is a blood test used to measure the level of vitamin B12 in the body, which is essential for the formation of red blood cells, proper nerve function, and DNA production. Low levels of vitamin B12 can lead to anemia, fatigue, weakness, numbness or tingling in the hands and feet, memory problems, and neurological disorders. Doctors may recommend this test for individuals with poor nutrition, vegetarian or vegan diets, digestive disorders, or symptoms of vitamin deficiency. The test helps diagnose vitamin B12 deficiency and guides appropriate treatment through dietary changes, supplements, or injections to maintain overall health and nervous system function.