Risk factor | Preferred approach to prevention |
Insufficient dietary intake: - Vegan or strict vegetarian diet
- Pregnancy or lactating with limited intake of animal protein
- Neonate breastfed by mother with vitamin B12 deficiency
| - Provide oral vitamin B12 supplementation:
- 2.4 mcg daily (adult RDA) or more is sufficient for most patients
- 2.6 mcg daily for pregnancy
- 2.8 mcg daily for breastfeeding
- Ensure that breastfeeding mothers are vitamin B12 replete
|
Inability to release vitamin B12 from food proteins (reversible causes): - Untreated chronic Helicobacter pylori infection
- Chronic anti-acid therapy:
- Antacids
- Proton pump inhibitors
- Histamine receptor 2 blockers
- Chronic excess alcohol use
| - Treat H. pylori infection
- Review need for chronic anti-acid therapy
- Reduce alcohol use
- Monitoring or supplementation may be appropriate for individuals who cannot reverse the underlying cause
|
Gastric/bariatric surgery* | Provide routine supplementation with either: - Oral vitamin B12 (350 to 1000 mcg daily)
- or
- IM (or deep subcutaneous) vitamin B12
- 1000 mcg per month (cyanocobalamin)
- or
- 1000 mcg every two to three months (hydroxocobalamin)
|
Inability to absorb vitamin B12-intrinsic factor complex: - Metformin use¶
- Pancreatic insufficiency
- Small intestinal bacterial overgrowth
- Small intestinal inflammation
- Small intestinal surgery
- Fish tapeworm infection
| - Treat reversible infections (bacterial overgrowth, tapeworm) or inflammation
- Monitor vitamin B12 levels (once a year is reasonable, test at any time if symptoms occur)
- Some patients may reasonably choose to take a supplement rather than undergo monitoring
|
Inactivation of vitamin B12 and inhibition of cofactor function: - Nitrous oxide¶ (inhalation anesthetic or recreational use)
| - Avoid nitrous oxide in susceptible individuals
- Perioperative monitoring of the CBC; maintain a low threshold to evaluate any abnormalities
- Maintain a low threshold for measuring vitamin B12 levels when evaluating neurologic or neuropsychiatric symptoms
- Sometimes these individuals have normal vitamin B12 levels but the vitamin is dysfunctional, and testing of MMA is required
|