What Does It Mean When Blood B12 Is High?

Recently, one of my patients showed me a high serum B12 level at 1105 pg/ml (normal 190-950 pg/ml). She is not taking B12 supplements. She was diagnosed with rheumatoid arthritis (RA) over 10 years. The following are my answer to her question.

Consumption of too many fortified foods. B12 is naturally present in foods of animal resources, including fish, meat, poultry, eggs, and dairy products. However, fortified cereals, plant milk, such as soy, almond, oat, cashew, and coconut milk, beverage, margarine, and nutritional yeast have a much higher bioavailable form than their food origin.

Cancer and inflammation of the liver. Extra B12 is stored in the liver until it is needed by the body. If a person stops consuming B12, the body's stores of this vitamin usually take about 5 years to exhaust. Cancer, alcohol, hepatitis, and drugs damage the liver cells, the stored B12 is released into the blood, and B12 from the food origin cannot be stored either.

Kidney diseases. B12 is a water-soluble vitamin, extra amount can be flushed out through urine. Medical conditions, such as diabetes, high blood pressure, lupus, and cancer cause kidneys to lose filtration function.

Autoimmune diseases and malignant blood disorders. Antibodies attack cell membrane and/or B12 binding protein, B12 cannot be released as a free form, thus cells are either not able to take in B12 or B12 is not be able cleared by the kidney.

When serum B12 is high, elevated blood homocysteine and/or methylmalonic acid level are signs of functional B12 deficiency. Further evaluations should be warranted to clarify the true cause of high serum B12.