FaridabadBy Dr B.C. Gupta, MD · 2026-09-01
A vitamin B12 test measures the amount of vitamin B12 in your blood. Vitamin B12 is needed to make red blood cells and to keep the nervous system working normally. It is one of the vitamins the body cannot make on its own, so it must come from food or supplements.
What does the test measure?
The test measures your serum vitamin B12 level, the amount of B12 circulating in your blood. It is often done along with a complete blood count because a low B12 level is one cause of anaemia. It may also be done with folate and ferritin, since B12, iron and folate each play a part in making healthy blood cells.
How to prepare
The sample is a blood draw. Fasting is usually not needed for B12 alone, but confirm with the laboratory whether the tests your doctor has ordered require it. Results are generally available the next day.
What a low level can mean
A low vitamin B12 level can cause tiredness, weakness, and a type of anaemia. It can also affect the nerves, leading to tingling or numbness in the hands or feet, and in some people difficulty with balance or memory. These symptoms can develop slowly, so a blood test is the reliable way to check your level. Your doctor will interpret the result along with your symptoms and other tests.
Who is it usually checked in?
Doctors often order a B12 test for people who are tired without an obvious cause, for older adults, for vegetarians and vegans, and for those on long term treatment that can lower B12 levels, such as metformin for diabetes, or that affects how the body absorbs it. It is also part of some anaemia workups and health packages.
This article is for general information only and is not medical advice. Always discuss your results and any health concerns with your doctor.
