Vitamin B12 (Serum) – Urinary Rate (24-Hour Collection)
This test measures how much vitamin B12 is naturally excreted in your urine over 24 hours. It helps assess how well your body absorbs vitamin B12, which is essential for nerve function and red blood cell production.
["This test can help diagnose vitamin B12 deficiency or malabsorption when other tests are inconclusive."]
Key facts at a glance
- LOINC
- 1460-5
- Short code
- Vit B12 p B12 24h Ur-mRate
- Synonyms
- Vit B12 p B12 24h Ur-mRate
- 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 Might Be Ordered
Your doctor may recommend this test if you have symptoms like fatigue, numbness, or weakness, or if standard vitamin B12 blood tests (like serum B12 levels) show borderline or unclear results. It’s also used in cases where other causes of deficiency, such as celiac disease or gastric surgery, are suspected.
What to Expect Before the Test
You’ll need to collect your urine for 24 hours, starting after your first morning urine void. Store the urine in a clean container and keep it refrigerated. Bring the entire sample to your lab appointment. Follow your doctor’s instructions carefully to ensure accurate results.
How the Test Works
The test measures the amount of vitamin B12 excreted in your urine over a full day. This helps determine how efficiently your body absorbs vitamin B12 from food. Abnormal results may indicate issues with absorption, such as pernicious anemia or other gastrointestinal disorders.
Possible Results and Their Meaning
Higher-than-expected rates might suggest overabsorption (rare) or lab error. Lower-than-expected rates could indicate vitamin B12 malabsorption, which may require further testing or dietary adjustments. Your doctor will interpret results in the context of your symptoms and other tests.
Reference range
NCBI: Vitamin B12 200-900 pg/mLN/A
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.
This test is particularly useful for diagnosing vitamin B12 deficiency when standard blood tests (like serum B12 or methylmalonic acid) are inconclusive. It helps rule out malabsorption disorders, such as atrophic gastritis or intestinal diseases, that can prevent proper vitamin B12 uptake. Low urinary excretion may also signal underlying gastrointestinal conditions that need medical evaluation.
Short name
Vitamin B12 Urinary Excretion Rate
Frequently asked questions
What Does a Low Vitamin B12 Urinary Rate Mean?
When Might I Need Follow-Up Testing?
Can Diet Affect This Test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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