What are the contraindications for Vitamin B12 (Cobalamin)?

From the Guidelines

Vitamin B12 supplementation is contraindicated in patients with a known hypersensitivity or allergy to vitamin B12, cobalt, or any components of the supplement formulation, as well as those with Leber's disease, polycythemia vera, and certain cobalt sensitivities. According to the most recent guidelines, patients with these conditions should exercise caution when considering vitamin B12 supplements 1.

Key Considerations

• Patients with a history of hypersensitivity or allergy to vitamin B12, cobalt, or any components of the supplement formulation should avoid vitamin B12 supplements altogether.
• Those with Leber's disease (hereditary optic nerve atrophy) should not take vitamin B12 as it may potentially worsen this condition.
• Patients with polycythemia vera should avoid B12 supplements as they can exacerbate this blood disorder by further increasing red blood cell production.
• Individuals with certain cobalt sensitivities should also exercise caution when considering vitamin B12 supplements.

Special Populations

• Pregnant and breastfeeding women should consult healthcare providers before supplementation.
• Patients receiving folate therapy for megaloblastic anemia without confirmed B12 deficiency require special consideration, as B12 deficiency could be masked.

General Guidance

Most vitamin B12 preparations are generally safe with few contraindications, but caution is warranted in these specific populations to prevent adverse reactions or worsening of underlying conditions, as highlighted in recent guidelines 1.

From the FDA Drug Label

Sensitivity to cobalt and/or vitamin B12 is a contraindication. The main contraindication for vitamin B12 is:

• Sensitivity to cobalt and/or vitamin B12 2

From the Research

Contraindications for Vitamin B12

• There are no direct contraindications for vitamin B12, but certain conditions may require caution when taking vitamin B12 supplements, such as:
  • Hypersensitivity to vitamin B12 or any of its components, as seen in a study on vitamin B12 hypersensitivity 3
  • Leber's hereditary optic neuropathy, as vitamin B12 deficiency may precipitate optic neuropathy in patients with this condition 4
• Certain medical conditions may also affect the absorption or metabolism of vitamin B12, such as:
  • Gastric or small intestine resections, inflammatory bowel disease, or use of certain medications like metformin or proton pump inhibitors, which may lead to vitamin B12 deficiency 5
  • Malabsorption syndromes, such as those occurring in familial pernicious anemia or after gastric surgery, which may require careful management of vitamin B12 levels 4
• It is essential to note that vitamin B12 deficiency can masquerade as various illnesses, and diagnosis may be challenging due to the lack of a robust absorption test and compromised sensitivity and specificity of other tests 6

Special Considerations

• Patients with elevated serum homocysteine levels and cardiovascular disease should not use vitamin B12 to reduce the risk of myocardial infarction or stroke, or alter cognitive decline, as it has been shown to be ineffective 5
• Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely to prevent deficiency 5
• Vegans or strict vegetarians should consume foods fortified with vitamin B12 or take vitamin B12 supplements to prevent deficiency, especially if they are older than 50 years 5