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Serum or plasma concentration of vitamin B12 (cobalamin)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of vitamin B12 in your blood. Vitamin B12 is essential for red blood cell production, nerve function, and DNA synthesis.

Quick summary

["Vitamin B12 helps prevent serious health issues like anemia and nerve damage."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
54164-9
Short code
CMV IE Ag Bld Ql
Synonyms
CMV IE Ag Bld Ql
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for vitamin B12 deficiency, which can occur due to poor diet, certain medical conditions, or issues with absorption in the gut. It may also be used to monitor treatment for conditions like pernicious anemia or to assess nutritional status.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn from a vein, but if it’s drawn from an arm or finger, eating or drinking is fine. Wear comfortable clothing if you’re having a blood draw.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm or draw blood from a finger. The process is quick and may cause a slight pinch. The blood sample is then sent to a lab for analysis.

What Are the Possible Results?

Results are compared to standard reference ranges for vitamin B12 levels in blood. Low levels may indicate deficiency, while high levels could suggest conditions like certain cancers or liver disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Vitamin B12 deficiency can result from poor dietary intake (e.g., vegan/vegetarian diets), malabsorption issues (e.g., pernicious anemia, celiac disease), or conditions affecting the stomach or intestines. Rarely, it may be due to kidney disease or certain medications.
What happens if my vitamin B12 level is low?
If your test shows low levels, your doctor may recommend dietary changes, supplements (oral or injectable), or further testing to identify the cause. Treatment aims to restore normal levels and prevent complications like nerve damage or anemia.
Can vitamin B12 levels be affected by other tests?
Yes, other tests like folate levels or methylmalonic acid (MMA) may be done together to assess vitamin B12 status. Some medications (e.g., metformin, proton pump inhibitors) can interfere with absorption, so your doctor may adjust recommendations accordingly.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy