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Vitamin B12 (Serum) with Immunoassay Method, 24-Hour Urine Collection

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

This test measures your vitamin B12 levels in your blood and checks how much is excreted in your urine over 24 hours. It helps assess vitamin B12 deficiency or malabsorption.

Quick summary

["Vitamin B12 is essential for nerve function and red blood cell production; low levels may cause fatigue or neurological issues."]

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

Key facts at a glance

LOINC
30906-2
Short code
Vit B12 p B12+IF 24h Ur-aCnc
Synonyms
Vit B12 p B12+IF 24h Ur-aCnc
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 This Test Is Done

Your doctor may order this test if you have symptoms like weakness, numbness, or unusual fatigue. It can also be used to diagnose conditions like pernicious anemia or celiac disease, which may affect how your body absorbs vitamin B12.

What to Expect Before the Test

For the blood draw, you’ll likely fast for 8–12 hours before your appointment. For the urine test, collect all urine over 24 hours in a special container. Follow your doctor’s instructions carefully.

Blood Test Process

A healthcare provider will draw blood from your arm. The process is quick and usually painless. You may feel a slight pinch, but it won’t take long.

Urine Test Process

You’ll need to start collecting your urine at a specific time (often midnight) and keep it in a container until the next day. Empty your bladder before starting, then collect all urine until you urinate again the following day.

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.

Low vitamin B12 levels in blood or urine may indicate deficiency, which can lead to anemia, nerve damage, or cognitive issues. High urine excretion could suggest kidney problems or certain metabolic disorders. This test helps guide treatment, such as supplements or dietary changes.

Short name

Vitamin B12 & Urine B12

Frequently asked questions

How long does the blood test take?
The blood draw itself takes only a few minutes, but results may take 1–3 business days to process and return.
Can I eat or drink anything before the urine collection?
Yes, but avoid special supplements or foods high in vitamin B12 unless instructed otherwise. Drink plenty of water to stay hydrated, but don’t alter urine color or consistency.
Will I need to do anything special with the urine sample?
Yes, keep the container clean and refrigerate it if not used immediately. Shake it gently before testing, and return it to your doctor on time to ensure accurate results.
  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