From the Guidelines
Vitamin B12 levels above 2000 pg/mL are not a desired outcome and may indicate excessive supplementation or an underlying medical condition. When vitamin B12 levels exceed 2000 pg/mL, it is essential to assess the cause, which could be due to excessive oral or injectable supplementation, or certain medical conditions such as myeloproliferative disorders, liver disease, or cancers [ 1 ].
Key Considerations
- High doses of oral B12 supplements (exceeding 1000-2000 mcg daily) or injectable B12 (cyanocobalamin or hydroxocobalamin) at doses of 1000 mcg or more can lead to elevated levels [ 1 ].
- Certain medical conditions can cause elevated B12 levels without supplementation, emphasizing the need for a thorough medical evaluation [ 1 ].
- The normal therapeutic target for B12 supplementation is typically between 300-900 pg/mL, not above 2000 pg/mL [ 1 ].
Recommendations
- If vitamin B12 levels are above 2000 pg/mL, it is crucial to consult with a healthcare provider to determine the cause and adjust the supplementation regimen as necessary [ 1 ].
- For patients undergoing bariatric surgery, guidelines recommend treating vitamin B12 deficiency immediately and providing maintenance treatment with 1 mg intramuscularly every 2–3 months lifelong [ 1 ].
- In cases of possible neurological involvement, such as unexplained sensory and/or motor and gait symptoms, seek urgent specialist advice from a neurologist and haematologist [ 1 ].
From the Research
Vitamin B12 Levels
- The normal range for vitamin B12 is typically considered to be between 200 and 900 pg/mL, however, the exact upper limit can vary depending on the laboratory and the specific test used.
- Levels above 2000 pg/mL are generally considered to be elevated, but the studies provided do not specifically address when vitamin B12 levels will be above 2000.
Elevated Vitamin B12 Levels
- Elevated vitamin B12 levels can be associated with various conditions, including solid neoplasia, hematological diseases, liver disorders, and excess vitamin B12 intake 2, 3.
- High serum levels of vitamin B12 can also be caused by monoclonal gammapathy of undetermined significance, renal failure, inflammatory or autoimmune diseases, and transient hematological disorders 3.
Treatment of Pernicious Anemia
- Oral vitamin B12 replacement at 1000 μg daily has been shown to be effective in replacing vitamin B12 levels in patients with pernicious anemia 4, 5.
- Studies have demonstrated that oral crystalline cyanocobalamin 1000 μg/d can increase serum cobalamin concentrations and improve clinical symptoms in patients with pernicious anemia 6, 5.
Vitamin B12 Supplementation
- Oral supplementation with 1000 μg/d of cyanocobalamin has been shown to improve vitamin B12 deficiency in pernicious anemia, with significant improvements in plasma vitamin B12, homocysteine, and methylmalonic acid concentrations 5.
- The median time to reverse initial vitamin B12 deficiency abnormalities ranged from 1 month for hemolysis to 4 months for mucosal symptoms 5.