Vitamin B12

Vitamin

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No Fasting Required

Details

Measures B12 levels critical for red blood cell production, nerve function, and DNA synthesis.

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Vitamin B12 Test - Comprehensive Information Guide

Why is it done?
- Measures the level of cobalamin (vitamin B12) in the bloodstream to assess nutritional status and detect deficiency states
- Diagnoses vitamin B12 deficiency anemia (pernicious anemia and megaloblastic anemia)
- Investigates symptoms such as fatigue, weakness, numbness, tingling, memory problems, and neurological complications
- Evaluates patients with gastrointestinal disorders affecting absorption (celiac disease, Crohn's disease, post-gastric surgery)
- Screens individuals on long-term medications that impair B12 absorption (metformin, proton pump inhibitors)
- Performed during evaluation of elevated homocysteine levels or metabolic concerns
- Typically ordered when patients present with macrocytic anemia or abnormal complete blood count findings
Normal Range
- Normal reference range: 200-900 picograms per milliliter (pg/mL) or 148-664 picomoles per liter (pmol/L)
- Reference ranges may vary slightly between laboratories based on testing methodology and population demographics
- Low B12 (< 200 pg/mL): Indicates deficiency requiring clinical evaluation and intervention
- Borderline low (200-300 pg/mL): May warrant further testing with methylmalonic acid and homocysteine levels to assess functional deficiency
- Normal range (300-900 pg/mL): Adequate B12 status; symptoms unlikely related to deficiency
- High B12 (> 900 pg/mL): Rare; may indicate supplementation, certain medications, or liver disease
Interpretation
- Low B12 levels with elevated methylmalonic acid and homocysteine indicates true B12 deficiency with reduced cellular function
- Intrinsic factor antibodies may be positive in pernicious anemia (autoimmune condition preventing B12 absorption)
- Vegetarian/vegan patients with low B12 suggest dietary insufficiency as B12 is primarily found in animal products
- Patients with gastrointestinal conditions (Crohn's disease, celiac disease, post-bariatric surgery) show malabsorption patterns
- Macrocytic anemia with low B12 indicates impaired red blood cell maturation and oxygen-carrying capacity compromise
- Neurological symptoms (paresthesias, ataxia, cognitive changes) may persist even after B12 repletion if deficiency was prolonged
- Factors affecting results: Recent blood transfusions, high-dose vitamin C supplementation, and certain medications may interfere with accurate measurement
Associated Organs
- Primary organ systems: Gastrointestinal tract (stomach, small intestine), nervous system, and hematopoietic system (bone marrow)
- Pernicious anemia: Autoimmune destruction of gastric parietal cells reducing intrinsic factor production needed for B12 absorption
- Megaloblastic anemia: Abnormal red blood cell production in bone marrow leading to large, immature RBCs with reduced function
- Peripheral neuropathy: Demyelination of peripheral nerves causing numbness, tingling, and weakness in extremities
- Subacute combined degeneration: Neurological condition affecting spinal cord white matter with potential permanent damage if untreated
- Cognitive impairment and dementia: B12 deficiency may contribute to memory loss, confusion, and psychiatric symptoms
- Associated conditions: Crohn's disease, celiac disease, post-gastrectomy, terminal ileum disease, and chronic pancreatitis affecting absorption
Follow-up Tests
- Methylmalonic acid (MMA) level: Elevated in B12 deficiency; helps confirm functional B12 deficiency when serum levels are borderline
- Homocysteine level: Elevated when B12 is deficient; useful metabolic marker for assessing functional B12 status
- Intrinsic factor and parietal cell antibodies: Test for autoimmune pernicious anemia to determine if B12 absorption is impaired
- Complete blood count (CBC): Evaluates hemoglobin, hematocrit, and RBC indices for macrocytic anemia confirmation
- Peripheral blood smear: Visualizes red blood cell morphology to confirm megaloblastic changes typical of B12 deficiency
- Folate level: Must be assessed concurrently as folate deficiency may coexist with B12 deficiency and cause similar anemia patterns
- Schilling test (rarely used): Historical test to determine if B12 malabsorption is due to intrinsic factor deficiency or ileal disease
- Gastroenterology consultation: Recommended if structural gastrointestinal abnormalities are suspected as cause of malabsorption
- Repeat B12 testing: Follow-up testing after 2-4 weeks of B12 therapy to assess treatment response and efficacy
Fasting Required?
- No fasting required: Vitamin B12 testing can be performed without fasting; food and fluids do not affect test accuracy
- Patient preparation: Routine blood draw procedures apply; ensure proper identification and verify test order prior to collection
- Medications: No medications need to be held before testing; however, certain medications (metformin, PPIs, H2-blockers) may affect B12 levels and should be documented
- Timing: B12 levels may be transiently elevated immediately after supplementation or injections; optimal testing is at least 3-4 days after last treatment
- Sample collection: Serum (blood) sample collected via standard venipuncture into appropriate collection tube; samples should be processed timely to prevent hemolysis
- Avoid delays: Samples should be sent to the laboratory promptly to ensure reliable results; prolonged storage may affect test accuracy

How our test process works!