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Serum or Plasma Vitamin B12 (Cobalamin) Concentration

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 or nerve damage."]

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

Key facts at a glance

LOINC
36778-9
Short code
MR Orbit-R
Synonyms
MR Orbit-R
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
mr
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It can also be used to check for vitamin B12 deficiency, especially in people with conditions like pernicious anemia, celiac disease, or those who follow strict vegetarian or vegan diets.

What to Expect During the Test

A small blood sample is taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The test is quick and done in a lab.

Possible Causes of Low or High Levels

Low vitamin B12 levels can result from poor diet, certain medications, or conditions affecting absorption in the gut. High levels are less common but may occur due to genetic disorders or certain medications.

What the Results Mean

Results help determine if you have a vitamin B12 deficiency or other related issues. Your doctor will interpret the results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 plays a critical role in maintaining energy levels, nerve function, and overall health. Deficiencies can lead to serious complications, including anemia, nerve damage, or cognitive issues. Regular monitoring may be recommended if you have conditions that affect vitamin B12 absorption.

Short name

Vitamin B12 Level

Frequently asked questions

What are the normal ranges for this test?
There isn’t a single standard range for vitamin B12 levels, as they can vary slightly between labs. Your doctor will use your specific results and overall health to guide treatment.
Can I eat or drink anything before this test?
You can eat and drink normally before the test unless your doctor instructs otherwise. Avoid alcohol for 24 hours before the test if recommended.
How long will it take to get my results?
Results are typically available within a few days to a couple of weeks, depending on your lab and healthcare provider’s process.
  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