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Vitamin B12 (Cobalamin) with Serum Immunoassay Confirmation

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

This test measures your levels of vitamin B12, a crucial nutrient needed for healthy red blood cells, nerve function, and DNA synthesis. Low levels may indicate deficiencies or underlying health conditions.

Quick summary

["Vitamin B12 helps prevent serious complications like anemia or nerve damage; check levels if you have fatigue, tingling, or other symptoms."]

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

Key facts at a glance

LOINC
6536-7
Short code
RABV Tiss Cult
Synonyms
RABV Tiss Cult
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
organism-specific-culture
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 weakness, numbness, or unusual fatigue, or if you have conditions like pernicious anemia, poor diet, or certain medications that affect vitamin B12 absorption. It’s also part of routine blood work for older adults or those with gastrointestinal issues.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any medications (like certain antibiotics or proton pump inhibitors) that might affect results. Avoid heavy meals 2 hours before testing for more accurate readings.

What the Results Mean

Results are interpreted by your healthcare provider based on your symptoms and medical history. Very low levels may require supplements or medical treatment, while normal levels suggest adequate vitamin B12 status.

Common Causes of Low or High Levels

Low vitamin B12 can stem from poor diet, malabsorption (e.g., from celiac disease or atrophic gastritis), or conditions like pernicious anemia. Rarely, high levels may indicate liver disease or certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 (Serum)

Frequently asked questions

What symptoms might I experience if my vitamin B12 levels are low?
Low vitamin B12 can cause fatigue, weakness, tingling in hands/feet, memory problems, or balance issues. Severe deficiencies may lead to nerve damage or anemia over time.
How long does it take to get results?
Results typically arrive within 1–3 business days, depending on lab processing times. Your doctor will discuss them with you during your follow-up visit.
Can I take vitamin B12 supplements without checking levels first?
No, supplements should only be taken under medical supervision. High doses can be harmful, and testing ensures you’re addressing the right cause of deficiency.
  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