Finding the Root Cause of B12 Deficiency
Placeholder: different causes need different replacement strategies.
- ~30%: Metformin users (placeholder low B12 risk)
- ~10-30%: PPI long-term use (placeholder reduced absorption)
- IF loss: Pernicious anemia (placeholder autoimmune cause)
- Direct loss: Ileal resection (placeholder absorption site removed)
Common causes overview
Placeholder: metformin, PPIs, pernicious anemia, and ileal disease each reduce B12 differently.
Scoring Malabsorption Severity
Placeholder: severity score guides route choice.
- 0-3: Mild severity (placeholder oral usually fine)
- 4-6: Moderate severity (placeholder oral with monitoring)
- 7-10: Severe severity (placeholder IM preferred)
- ~8-12 wk: Reassessment (placeholder recheck levels)
Severity scoring basis
Placeholder: labs, symptoms, and cause combine into a severity score.
High-Dose Oral Cyanocobalamin — Passive Diffusion Route
Placeholder: high doses push enough B12 through passive diffusion.
- ~1%: Passive diffusion (placeholder of oral dose absorbed)
- 1000-2000 mcg: Typical dose (placeholder daily oral dose)
- Yes: IF-independent (placeholder bypasses IF gate)
- Mild-moderate: Best for (placeholder severity cases)
Oral pathway mechanism
Placeholder: high concentration gradient drives passive gut absorption.
Intramuscular Injection — Direct Reservoir Filling
Placeholder: IM injection bypasses gut entirely and fills the bloodstream.
- ~100%: Bioavailability (placeholder injected dose)
- 1mg IM: Typical schedule (placeholder loading then monthly)
- Severe cases: Best for (placeholder or neuro symptoms)
- High: Reliability (placeholder independent of gut)
IM pathway mechanism
Placeholder: injection deposits B12 directly into muscle then blood.
Choosing a Maintenance Therapy Route
Placeholder: maintenance route depends on response and cause reversibility.
- Oral ok: Reversible cause (placeholder e.g. metformin/PPI)
- IM ok: Irreversible cause (placeholder e.g. pernicious anemia)
- 3-6 mo: Monitoring interval (placeholder recheck levels)
- No response: Switch trigger (placeholder escalate to IM)
Maintenance decision summary
Placeholder: match maintenance route to severity trend and cause.
Placeholder: reassess route if levels fail to normalize.