From the Guidelines
High B12 levels in the blood are generally not a health concern in themselves, but may indicate an underlying condition that requires attention, and according to the most recent evidence, supplementation with B vitamins, including B12, is reasonable to reduce stroke risk 1. When considering the management of high B12 levels, it's essential to prioritize the underlying cause rather than the elevated B12 level itself. Common causes of high B12 levels include:
- Supplementation (multivitamins, B-complex vitamins, or B12 injections)
- Liver disease
- Certain blood disorders like myeloproliferative disorders
- Kidney disease
- Certain cancers Unlike low B12, which requires treatment, high B12 typically doesn't need specific treatment beyond addressing the underlying cause. The recent American Heart Association guideline on secondary stroke prevention suggests that B vitamins, including B12, can lower homocysteine levels and prevent stroke 1. Therefore, it is recommended to continue any prescribed medications and consult with your healthcare provider to determine the cause of the elevated B12 level, and consider supplementation with B vitamins, including B12, to reduce stroke risk, as supported by the highest quality evidence from the 2022 study published in Stroke 1. Additional tests such as liver function tests, complete blood count, or kidney function tests may be recommended to identify the underlying cause. It's also important to note that high B12 levels themselves don't cause symptoms, so any symptoms you're experiencing are likely related to the underlying condition rather than the B12 level itself.
From the Research
High B12 Levels and Associated Conditions
- High B12 levels have been associated with various conditions, including liver disease and cancer 2, 3, 4, 5, 6
- A study published in 2017 found that falsely elevated serum vitamin B12 levels were associated with the severity and prognosis of chronic viral liver disease 2
- Another study published in 2020 found that elevated plasma vitamin B12 levels were associated with the presence of solid cancer, particularly in cases of metastases 3
Liver Disease and B12 Levels
- Vitamin B12 is stored primarily in the liver, and highly elevated serum vitamin B12 levels can occur in acute hepatitis and severe alcoholic liver disease 2
- A study published in 2014 found that vitamin B12 and its binding proteins were elevated in patients with hepatocellular carcinoma and chronic liver diseases 6
- However, another study published in 2022 found that the association between plasma vitamin B12 concentrations and liver cancer was not consistent across studies 4
Cancer and B12 Levels
- Elevated plasma vitamin B12 levels have been associated with an increased risk of solid cancer, particularly in cases of metastases 3
- However, a study published in 2022 found that there was no evidence for a causal relationship between high plasma vitamin B12 levels and cancer 4
- Another study published in 2024 found that methylmalonic acid, rather than vitamin B12, was associated with an increased risk of mortality in patients with metabolic dysfunction-associated steatotic liver disease 5
Joint Association of B12 and Methylmalonic Acid
- A study published in 2024 found that the joint association of high levels of methylmalonic acid and vitamin B12 showed the strongest associations with all-cause and cardiovascular disease mortality 5
- The joint effect was modified by serum folate, suggesting a potential interaction between these nutrients 5