From the Guidelines
Vitamin B12 deficiency treatment should be tailored to the underlying cause, with a focus on preventing irreversible neurological damage and improving quality of life. The most common causes of vitamin B12 deficiency include dietary deficiency, malabsorption due to pernicious anemia or gastrointestinal disorders, surgical causes such as gastric bypass or ileal resection, and medication-induced deficiency from proton pump inhibitors or metformin.
- For dietary deficiency, daily oral supplementation with cyanocobalamin 1000-2000 mcg is recommended, along with increased consumption of B12-fortified foods 1.
- For malabsorption due to pernicious anemia or gastrointestinal disorders, intramuscular injections are typically required, with a regimen of hydroxocobalamin 1 mg intramuscularly on alternate days until there is no further improvement, then hydroxocobalamin 1 mg intramuscularly every 2 months 1.
- Patients with surgical causes, such as gastric bypass or ileal resection, also require lifelong parenteral therapy, with a recommended dose of 1000 mg of vitamin B12 by intramuscular injection every month for life 1.
- For medication-induced deficiency, oral supplementation at 1000 mcg daily is usually sufficient while addressing the medication issue 1. It is essential to monitor treatment efficacy through symptom improvement and normalization of blood levels, typically within 4-8 weeks, and to seek urgent specialist advice from a neurologist and haematologist if there is possible neurological involvement 1. Intramuscular injections of hydroxocobalamin are the preferred treatment for vitamin B12 deficiency, especially in cases with neurological involvement, due to their high efficacy and safety profile 1.
From the FDA Drug Label
Cyanocobalamin is indicated for vitamin B12 deficiencies due to malabsorption which may be associated with the following conditions: Addisonian (pernicious) anemia Gastrointestinal pathology, dysfunction, or surgery, including gluten enteropathy or sprue, small bowel bacteria overgrowth, total or partial gastrectomy Fish tapeworm infestation Malignancy of pancreas or bowel Folic acid deficiency Requirements of vitamin B12 in excess of normal (due to pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease) can usually be met with oral supplementation.
The causes of vitamin B12 deficiency include:
- Malabsorption due to conditions such as Addisonian (pernicious) anemia, gastrointestinal pathology, dysfunction, or surgery
- Gastrointestinal conditions like gluten enteropathy or sprue, small bowel bacteria overgrowth, total or partial gastrectomy
- Infections like fish tapeworm infestation
- Malignancy of pancreas or bowel
- Folic acid deficiency
- Increased requirements due to pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease 2 Treatment options for different causes of vitamin B12 deficiency include:
- Surgical correction of anatomic lesions leading to small bowel bacterial overgrowth
- Expulsion of fish tapeworm
- Discontinuation of drugs leading to vitamin malabsorption
- Gluten-free diet in nontropical sprue
- Administration of antibiotics in tropical sprue
- Oral supplementation for increased requirements due to pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease 2
From the Research
Causes of Vitamin B12 Deficiency
- Inadequate intake of vitamin B12-containing animal-derived foods 3
- Inadequate bioavailability of vitamin B12 3
- Malabsorption of vitamin B12, which can occur after gastric surgery for obesity or other conditions 4, 5
- Disruption of vitamin B12 transport in the blood or impaired cellular uptake or metabolism 3
- Autoimmune diseases, such as pernicious anemia, which can cause chronic atrophic gastritis and cobalamin deficiency 6
Treatment Options for Different Causes of Vitamin B12 Deficiency
- For patients with vitamin B12 deficiency after gastric surgery for obesity, oral doses of crystalline vitamin B12 of at least 350 µg per day can correct low serum vitamin B12 levels in 95% of patients 4
- For patients with pernicious anemia, vitamin B12 replacement therapy is straightforward, but prompt recognition of symptoms is vital to prevent irreversible neurologic sequelae 6
- For patients undergoing bariatric surgery, preventive strategies include lifelong supplementation with vitamin B12, with intramuscular vitamin B12 being the gold standard of therapy, especially in symptomatic patients 5
- High-dose oral cyanocobalamin may be considered for asymptomatic patients with vitamin B12 deficiency after Roux-en-Y gastric bypass, especially when there are concerns with adherence to intramuscular therapy 5
- A systematic review and network meta-analysis found that all routes of administration of vitamin B12 (oral, intramuscular, and sublingual) can effectively increase vitamin B12 levels, but the intramuscular route was ranked first, followed by the sublingual route 7
Key Recommendations
- Patients undergoing bariatric surgery must be continuously educated on proper nutrition, the risk of developing significant vitamin B12 deficiency, and the role of supplements in avoiding catastrophic consequences 5
- Diagnostic biomarkers for vitamin B12 status include decreased levels of circulating total vitamin B12 and transcobalamin-bound vitamin B12, and abnormally increased levels of homocysteine and methylmalonic acid 3