Vitamin B12 testing measures the level of that vitamin in your blood. Having a vitamin B12 deficiency, or a low level of this essential vitamin, can cause a range of health issues, including anemia and nervous system problems. Adequate levels of vitamin B12 are needed for your body to maintain a healthy nervous system, make red blood cells, and create DNA, the genetic material in all of our cells.
A vitamin D test measures the level of vitamin D in your blood to make sure you have enough for your body to work well. Vitamin D is essential for healthy bones and teeth. It also helps keep your muscles, nerves, and immune system working normally. Having low levels of vitamin D is a common problem that can lead to bone disorders and other medical problems.