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Vitamin B12 (Cobalamin) Blood Test

The Vitamin B12 Blood Test measures the level of cobalamin in your blood. Vitamin B12 is essential for red blood cell formation, DNA synthesis, healthy nerve function, and methylation. Suboptimal B12 can contribute to fatigue, weakness, numbness or tingling, memory or mood changes, and—when prolonged—megaloblastic anemia. In the PlexusDx Nutrition Deficiency Blood Test, B12 is interpreted alongside complementary markers to give a more complete picture of nutritional status.

Why Measure Vitamin B12?

  • Energy & hematology: B12 is required to produce healthy red blood cells; low levels can lead to anemia and fatigue.
  • Neurologic health: Supports myelin integrity and normal nerve signaling; insufficiency may cause paresthesias or cognitive changes.
  • Methylation balance: Partners with folate to recycle homocysteine to methionine, supporting one-carbon metabolism.
  • Nutritional screening: Useful for people at higher risk of low intake or absorption (older adults, certain medications, plant-based diets, GI conditions).

How the PlexusDx Test Works

  • At-home collection: Simple finger-prick kit with a prepaid return mailer.
  • Fast turnaround: Clear, digital results typically available within ~2 business days of lab receipt.
  • Direct access: Order online; generally HSA/FSA eligible.

Understanding Results (High-Level)

  • Within range: Suggests adequate B12 for blood and neurologic needs.
  • Low or borderline: May contribute to elevated homocysteine, anemia, fatigue, neuropathy, or cognitive changes. Your clinician may consider diet review, absorption issues, and follow-up testing.
  • High: Often reflects supplementation; interpret in clinical context, especially if symptoms persist.

What Can Influence Vitamin B12 Levels?

  • Dietary intake: B12 is naturally found in animal-derived foods (fish, dairy, eggs, meat) and fortified plant foods.
  • Absorption factors: Low stomach acid, intrinsic factor deficiency, and GI conditions (e.g., celiac disease, IBD) can reduce absorption.
  • Medications: Long-term use of metformin, proton-pump inhibitors/H2 blockers, and certain other drugs can lower B12 over time.
  • Lifestyle & life stage: Vegan/vegetarian diets without fortified foods or supplements, heavy alcohol use, and aging increase risk of insufficiency.
  • Genetics: Variants affecting B12 transport or folate cycle enzymes can increase functional B12 needs.

How to Support Healthy B12 Levels

  • Nutrition first: Include B12-rich foods (salmon, sardines, dairy, eggs, lean meats) or fortified alternatives if plant-based.
  • Targeted supplementation: Discuss form and dose with your clinician:
    • Methylcobalamin — active form used in methylation.
    • Hydroxocobalamin — longer-acting option often used clinically.
    • Cyanocobalamin — stable, widely available form.
  • Address root causes: Review GI health, medications, alcohol intake, and co-nutrients (folate, B6, riboflavin, choline).
  • Re-testing: After dietary or supplement changes, re-check per your clinician’s plan to confirm improvement.

FAQs

My B12 is “normal” but I still have symptoms—now what?
Your clinician may consider complementary markers (e.g., homocysteine as part of your panel) plus your history, diet, and medications.

I’m plant-based—how can I maintain B12?
Use fortified foods (plant milks, nutritional yeast, cereals) and consider a B12 supplement. Periodic screening helps ensure adequacy.