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Vitamin B12 (Serum or Plasma Concentration)

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

This test measures the amount of vitamin B12 (also called cobalamin) in your blood. Vitamin B12 is essential for nerve function, red blood cell production, 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 17, 2026Editorial policy

Key facts at a glance

LOINC
54378-5
Short code
Vit B12 Ur-sCnc
Synonyms
Vit B12 Ur-sCnc
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
200
Ref high
900
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order a vitamin B12 test if you have symptoms like fatigue, weakness, numbness in hands or feet, dizziness, or a loss of appetite. It may also be checked if you have conditions like pernicious anemia, gastrointestinal disorders, or if you’re on certain medications that can interfere with vitamin B12 absorption.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood sample drawn from a vein in your arm, or in some cases, a urine sample may be collected. If you’re on certain medications (like metformin), let your doctor know before the test.

What the Results Mean

Results are used to diagnose deficiencies, monitor treatment, or check for conditions affecting vitamin B12 absorption. Low levels may indicate a deficiency, while high levels could be due to certain medical conditions or medications.

Common Conditions Linked to Vitamin B12 Levels

Low vitamin B12 levels can cause anemia, nerve damage, or cognitive issues. High levels might suggest conditions like vitamin B12 toxicity (rare) or certain liver or kidney disorders. Your doctor will interpret results in the context of your symptoms and medical history.

Reference range

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

Specimen: urine

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 causes vitamin B12 deficiency?
Vitamin B12 deficiency can result from poor diet (e.g., vegan/vegetarian diets without fortified foods), conditions affecting absorption (like atrophic gastritis or pernicious anemia), or certain medications. Lifestyle factors, such as smoking or alcohol use, may also contribute.
How can I improve my vitamin B12 levels if they’re low?
If your levels are low, your doctor may recommend dietary changes (e.g., fortified foods, supplements, or injections). Follow-up tests may be needed to monitor your response to treatment.
Is there a difference between serum and plasma vitamin B12 tests?
Both tests measure the same analyte, but plasma is blood without clotting factors, while serum is blood after clotting. Your doctor will specify which type is needed based on your clinical situation.
  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