Skip to content

Vitamin B12 (Serum or Plasma Concentration)

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

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

Quick summary

["Check your vitamin B12 levels to ensure proper nerve health and prevent deficiencies."]

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

Key facts at a glance

LOINC
105143-2
Short code
MRA C-spine ves
Synonyms
MRA C-spine ves
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-angio
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 This Test Is Done

Your doctor may order this test if you have symptoms like numbness or tingling in your hands and feet, weakness, memory problems, or unusual fatigue. It can also be used to diagnose conditions like pernicious anemia, which occurs when your body can’t absorb enough vitamin B12 from food.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. If you’re on a vitamin B12 supplement or have had recent injections, your doctor may ask you to stop temporarily.

What the Results Mean

Low levels of vitamin B12 may indicate a deficiency, which can affect how your body uses energy and maintains nerve function. High levels are less common but could signal certain medical conditions or over-supplementation.

Common Conditions Linked to Vitamin B12 Deficiency

A deficiency in vitamin B12 can lead to anemia, nerve damage, or cognitive issues. Conditions like celiac disease, Crohn’s disease, or atrophic gastritis (stomach lining thinning) can reduce vitamin B12 absorption.

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?
Low vitamin B12 levels can result from poor diet (low intake of meat, eggs, or dairy), conditions that interfere with absorption (like pernicious anemia or celiac disease), or certain medications that reduce stomach acid or absorption.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab. Your doctor will discuss the findings with you during your follow-up visit.
Can I take vitamin B12 supplements without checking my levels first?
It’s best to avoid high-dose vitamin B12 supplements without medical advice, as excessive intake can sometimes mask symptoms of other deficiencies or lead to imbalances. Always consult your doctor before starting supplements.
  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