Skip to content

Vitamin B12 (Serum or Plasma Mass Concentration)

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

This test measures the amount of vitamin B12 in your blood, an essential nutrient for nerve function and red blood cell production.

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
17527-3
Short code
Vit A Free SerPl-mCnc
Synonyms
Vit A Free SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 in people with conditions like pernicious anemia, celiac disease, or those on certain medications that may interfere with vitamin B12 absorption.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring any medications you’re currently taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The process is quick and typically painless. You may feel a slight pinch, but the area will numb quickly.

What Are Possible Results?

Results are compared to a general reference range for healthy adults. Very low levels may indicate deficiency, while very high levels could suggest conditions like certain cancers or autoimmune disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to megaloblastic anemia, neurological issues, or cognitive problems. High levels may require further evaluation to rule out underlying conditions like chronic kidney disease or certain cancers. Early detection and treatment can prevent long-term complications.

Short name

Vitamin B12 Level

Frequently asked questions

How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your symptoms, medical history, and other test results. People with known deficiencies or risk factors may need monitoring more frequently.
What Does a Low or High Vitamin B12 Level Mean?
A low level may mean you’re not getting enough vitamin B12 from your diet or your body isn’t absorbing it properly. A high level could indicate an unrelated issue, but further testing may be needed to explore causes like autoimmune diseases or certain medications.
Can I Take Supplements to Fix a Low Vitamin B12 Level?
Yes, vitamin B12 supplements or injections can help restore levels. Your doctor may recommend oral supplements, injections, or nasal sprays depending on the cause of your deficiency. Follow their guidance for the best approach.
  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