Vitamin B12 Test
A vitamin B12 test measures the amount of cobalamin circulating in your blood. B12 supports healthy nerves and the making of red blood cells, and this is one of the markers clinicians use to help evaluate B12 status.
About this test
Vitamin B12, also called cobalamin, is a water-soluble vitamin the body relies on for healthy nerve cells, the formation of red blood cells, and the making of DNA. The body cannot produce it on its own, so it comes from the diet — mainly animal-based foods — and is absorbed through a multi-step process in the stomach and small intestine.
The test is done with a simple blood draw at a patient service center. A phlebotomist collects a sample from a vein in the arm, and it is sent to the laboratory.
Who might consider this test?
- Others consider it because of factors that can affect how much B12 the body takes in
- Following a vegetarian or vegan pattern of eating
Test details
| Quest code | 927 |
|---|---|
| Methodology | Immunoassay |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
Related tests and panels
A fast, on-the-go check of four essential nutrients that impact your energy,…
Groups markers clinicians review when looking into persistent fatigue, low…
Measures markers related to cognitive health, including nutrients, thyroid and…
Quest resources
Additional details
What this test looks at
A B12 test reports how much cobalamin is present in a blood sample. B12 plays a behind-the-scenes role in keeping nerve cells healthy and in helping the bone marrow build red blood cells, so when it runs low the effects can show up in energy, sensation, and thinking. Measuring the circulating amount gives a clinician a starting reference for whether B12 might be part of what a person is experiencing.
It helps to remember that a single B12 measurement describes one moment in time. The amount in the blood does not always mirror how much is available inside the cells, which is one reason a clinician may look at related markers before drawing any conclusions.
How clinicians use B12 in context
B12 is frequently interpreted alongside other markers. Folate is a common companion because the two vitamins work together in overlapping pathways. When a clearer picture is needed, a clinician may also consider markers such as homocysteine or methylmalonic acid, which can shift when B12 is in short supply and can help clarify a borderline result. Read together, these markers say more than any one of them can alone.
Results are meant to guide a conversation, not to stand in for one. A clinician weighs the measurement against diet, medications, other lab work, and the symptoms a person describes before deciding whether anything further is worth considering.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does a vitamin B12 test measure?
It measures the amount of vitamin B12, also called cobalamin, circulating in the blood. B12 supports nerve health and the formation of red blood cells, and the measurement gives a clinician one piece of information about B12 status.
Who commonly orders a B12 test?
People exploring symptoms such as fatigue, tingling in the hands or feet, or brain fog often talk with a clinician about it, as do those following plant-based diets or living with conditions that can affect how B12 is absorbed.
How is the sample collected?
Through a routine blood draw at a patient service center. A phlebotomist takes a small sample from a vein in the arm and sends it to the laboratory for analysis.
Do I need to fast before a B12 test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Is B12 ever measured with other markers?
Yes. Clinicians often pair it with folate, and sometimes with homocysteine or methylmalonic acid, to get a fuller view of B12 status and to help interpret a borderline result in context.
How much does the Vitamin B12 test cost?
The cash price at Celio Health is $20. That covers the physician's order and sample collection at a Quest patient service center — no insurance is needed and there's no separate doctor's visit to pay for.