Vitamin B12, or cobalamin, is an important nutrient that helps your body function. It plays a role in nerve function, the production of red blood cells, and the creation of DNA. A blood test measures the amount of B12 in your system, and while a low level often signals a deficiency, having an elevated B12 level can also occur and warrants understanding.
Understanding Your B12 Levels
Normal B12 levels for adults typically fall within a range of about 200 to 900 picograms per milliliter (pg/mL). A high B12 result means your level exceeds the upper limit of this normal range, often considered above 900 pg/mL. These reference ranges can vary slightly between different laboratories. Your healthcare provider will interpret your specific test results in the context of your overall health.
Common Causes of Elevated B12
One of the most frequent reasons for elevated B12 levels is dietary intake. Many common foods are rich sources of this vitamin, including meat, fish, poultry, eggs, and dairy products. Regularly consuming these foods contributes to your body’s B12 supply.
Taking B12 supplements, especially in high doses, can significantly increase levels. Similarly, consuming fortified foods like breakfast cereals and nutritional yeasts, which have B12 added to them, can also contribute to elevated levels. Additionally, individuals receiving intramuscular B12 injections for deficiency treatment will typically experience a temporary but substantial rise in their B12 levels. Since B12 is water-soluble, your body usually excretes any unneeded excess through urine. However, the liver stores a considerable amount of B12, and this stored supply can also influence blood levels.
Medical Conditions Associated with High B12
While often linked to diet or supplements, high B12 levels can sometimes point to underlying medical conditions. Liver diseases are a common association because the liver stores a large portion of the body’s B12. Conditions such as cirrhosis, hepatitis, and liver cancer can lead to damaged liver cells releasing stored B12 into the bloodstream.
Kidney disease can also contribute to elevated B12 levels. Impaired kidney function may reduce the body’s ability to excrete B12, leading to its accumulation in the blood.
Certain blood disorders, known as myeloproliferative disorders, including chronic myeloid leukemia (CML) and polycythemia vera, are also associated with high B12. These conditions can cause an overproduction of certain blood cells, which in turn leads to an increase in B12-binding proteins, elevating circulating B12 levels.
Some solid tumors have been linked to elevated B12 levels, including cancers of the lung, pancreas, prostate, and certain liver cancers. In these cases, the elevated B12 might be due to the tumor producing B12-binding proteins or the disease process affecting B12 metabolism. A high B12 level alone does not confirm these conditions, but it can signal a need for further investigation.
Next Steps After a High B12 Result
If you receive a high B12 result, consulting with a healthcare professional is an important next step. They can help interpret the result within the context of your overall health and medical history. While a high B12 level is frequently benign, medical evaluation can help rule out any underlying issues.
Discuss all medications and supplements you are currently taking with your doctor, including B12 supplements, multivitamins, or fortified foods, as these are common contributors to elevated levels. Your doctor might recommend additional tests to investigate potential underlying causes if they suspect a medical condition. These further tests could include evaluating liver and kidney function or conducting more specific blood tests if a blood disorder is suspected. In some cases, your doctor may suggest monitoring your B12 levels over time to see if they naturally decrease or remain stable.