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Vitamin B12 (Cobalamin) with Immunoassay Probe Measurement

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

This test measures the level of vitamin B12, an essential nutrient needed for healthy nerve function and red blood cell production.

Quick summary

["Low vitamin B12 can cause fatigue, numbness, or nerve problems; high levels may indicate certain conditions requiring medical attention."]

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

Key facts at a glance

LOINC
90886-3
Short code
FLUBV RNA Ct Spec Qn NAA+probe
Synonyms
FLUBV RNA Ct Spec Qn NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
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 to check for vitamin B12 deficiency, which can lead to anemia or nerve damage. It’s often done if you have symptoms like weakness, tingling, or unusual fatigue, or if you have conditions like pernicious anemia, celiac disease, or poor diet.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw if instructed by your healthcare provider. Bring any medications you’re currently taking.

How the Test Works

A small sample of blood is taken from a vein in your arm. The blood is then analyzed using an immunoassay to detect vitamin B12 levels in your serum or plasma.

What the Results Mean

Results help determine if your vitamin B12 levels are too low, normal, or too high. Low levels may require supplements or medical treatment, while high levels could signal underlying conditions like certain cancers or liver disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 (Serum/Plasma)

Frequently asked questions

What are the normal reference ranges for this test?
Reference ranges can vary by lab and may not be provided to you directly. Your doctor will interpret the results in the context of your health and symptoms. Low levels may trigger further testing or treatment.
Can vitamin B12 levels change over time?
Yes, vitamin B12 levels can fluctuate due to diet, medication use, absorption issues, or underlying health conditions. Regular monitoring may be needed if you have a history of deficiency or risk factors.
Is there anything I should avoid before this test?
Avoid excessive alcohol or certain medications (like certain antibiotics or proton pump inhibitors) that may affect vitamin B12 absorption. Follow your doctor’s instructions for fasting if required.
  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