Serum Vitamin B12 (Cobalamin) (B12)
Vitamin B12 is an essential cobalt-containing cofactor required for methionine synthase (homocysteine remethylation) and methylmalonyl-CoA mutase (fatty acid energy production).
Standard vs. Optimal Reference Rangespg/mL
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
200 - 900 pg/mL
General reference distribution across unselected commercial populations.
500 - 900 pg/mL (with MMA < 0.20 μmol/L)
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
B12 bound to gastric intrinsic factor is absorbed in the terminal ileum. As a cofactor, methylcobalamin transfers methyl groups from 5-MTHF to homocysteine, producing methionine for S-adenosylmethionine (SAMe) methylation reactions.
Differential Diagnosis
Elevated Levels (B12 High)
- •Excessive parenteral or high-dose oral supplementation
- •Myeloproliferative disorders / Acute leukemia
- •Severe liver cirrhosis (release of stored cobalamin)
Low Levels (B12 Low)
- •Pernicious anemia (anti-intrinsic factor or anti-parietal cell antibodies)
- •Strict vegan or vegetarian diet without supplementation
- •Atrophic gastritis / Long-term PPI or Metformin therapy
- •Terminal ileal resection or Crohn disease
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
Standard 10 to 12 hour overnight fast is recommended; avoid high-dose vitamin and mineral supplements for 24 hours prior to blood draw. Protect light-sensitive specimens (such as Vitamin B6, B12, and Folate) from ultraviolet light exposure by using amber collection tubes. Centrifuge and separate serum or plasma promptly to prevent in vitro leakage of intracellular minerals (e.g. magnesium, potassium) from red blood cells.
Reflexive Testing Protocol:
- Functional metabolic surrogate markers (Methylmalonic Acid for B12, Homocysteine for B6/B12/Folate, Red Blood Cell Magnesium)
- Complete Metabolic Panel and Ionized Calcium to evaluate electrolyte and mineral balance
- Celiac disease serology (Tissue Transglutaminase IgA with Total IgA) to screen for occult enteropathic malabsorption
- Parathyroid Hormone (PTH) and 24-Hour Urine Calcium quantification in cases of abnormal Vitamin D or calcium homeostasis
- Comprehensive Nutritional & Heavy Metal Trace Element panel via ICP-MS if multiple deficiencies are present
Clinical Citations & Primary Literature (1)
- [1]Vitamin B12 Deficiency: Recognition, Prevention, and Clinical Management - New England Journal of Medicine (2021). PMID: 34161704
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Serum Vitamin B12 (Cobalamin) (B12) into overall healthspan optimization.