A vitamin B12 test measures the amount of vitamin B12 in your blood, which is essential for maintaining healthy nerve cells and producing DNA and red blood cells. Low levels of vitamin B12 can lead to serious health issues such as anaemia, fatigue, weakness, nerve damage, and cognitive problems like memory loss and difficulty thinking clearly. Since vitamin B12 is crucial for energy, mood, and overall brain function, a deficiency can significantly impact your quality of life. By taking a vitamin B12 test, you can identify deficiencies early and take steps to correct them, ensuring you maintain good health and prevent potential long-term complications.