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Vitamin B12 (Serum) Concentration

Published: August 9, 2026Updated: August 17, 2026

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

Quick summary

["Vitamin B12 helps prevent anemia and supports brain and nerve health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
54376-9
Short code
Vit B12 Fld-sCnc
Synonyms
Vit B12 Fld-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
200
Ref high
900
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, or if you have conditions like pernicious anemia, poor diet, or certain medications that may interfere with vitamin B12 absorption.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or hand to draw blood. If you’re on certain medications (like metformin), let your doctor know before the test.

What the Results Mean

Results help determine if your vitamin B12 levels are too low, normal, or too high. Low levels may indicate deficiencies or underlying health issues requiring treatment.

Common Causes of Low Vitamin B12

Deficiencies can stem from poor diet (e.g., veganism), malabsorption issues (like pernicious anemia), or long-term use of certain medications.

Reference range

NCBI: Vitamin B12 200-900 pg/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What Might My Doctor Ask?
Your doctor may ask about your diet, symptoms, medications, or family history of vitamin B12 deficiencies to guide further testing or treatment.
How Often Should I Get This Test?
If you have a known deficiency or risk factors, your doctor may recommend regular monitoring. Otherwise, tests are typically done only when symptoms or concerns arise.
Can I Take Supplements Instead?
Supplements can help, but your doctor may still need to monitor levels to ensure proper absorption and avoid overuse.
  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 17, 2026. · Read our editorial policy