Elevated Vitamin B12 Levels May Signal Hidden Disease

Oct 10, 2025 - 09:54 Updated: Oct 9, 2025 - 16:40

Elevated Vitamin B12 Levels May Signal Hidden Disease

Vitamin B12 is a vital nutrient that keeps the body running.

Without enough of it, people can develop anemia, fatigue, brain and nerve problems, and even cognitive decline. Most people get enough vitamin B12 from their diet or supplements.

However, what happens when B12 levels are unusually high?

“Abnormally high blood B12 levels are often not caused by taking too much. Instead, they may reflect underlying diseases or metabolic problems,” Dr. Wenjie Bi, a medical practitioner at the University of Tokyo, told The Epoch Times.

Elevated B12 Levels Raise the Risk of Serious Diseases

Persistent elevation can be a warning signal tied to hidden problems in the liver, kidneys, blood, immune system, or even cancer.

Liver Disease

Diseases such as cirrhosis, fatty liver, and hepatitis may lead to elevated B12 levels.

The liver is the body’s main storage site for vitamin B12. When liver cells are damaged, stored B12 can leak into the blood. At the same time, the liver may not process or clear B12 as it should, causing levels to climb. Some of this excess B12 is “inactive,” meaning it cannot be used by the body.

However, high B12 levels do not automatically suggest liver disease. It should be interpreted together with other test results and symptoms. Signs such as jaundice, fatigue, a swollen abdomen, or loss of appetite—combined with abnormal liver function tests—make it more likely that the elevated B12 suggests a liver problem, in which case a doctor should check liver health.

Kidney Failure

The kidneys normally help filter B12 from the blood. When they fail, the vitamin accumulates.

When the kidneys do not function properly, the body cannot filter vitamin B12 effectively, Dr. Jingduan Yang, CEO of New York Northern Medical Center, told The Epoch Times. As a result, the vitamin builds up in the blood. Over time, persistently high B12 levels may be an early sign of kidney disease.

A study has found that serum B12 levels higher than 900pg/mL are associated with a 2.8-fold higher risk of acute kidney damage compared with normal levels.

Yang noted that patients should pay attention if high B12 levels are accompanied by warning signs such as less urine, changes in urine color, swelling around the ankles or eyes, fatigue, dizziness, or loss of appetite. In these cases, he said, it’s important to get kidney function checked promptly.

Blood or Bone Marrow Diseases

Chronic myeloid leukemia, multiple myeloma, and polycythemia vera may also cause elevated B12 levels. This is because these diseases increase B12-binding proteins in the blood, thereby causing abnormally high serum B12 levels.

One example comes from a Latvian cohort study involving more than 79,000 patients. Researchers followed patients with extremely elevated B12 levels (greater than 1,700 pg/mL) and compared them with controls. The findings were alarming: people with very high B12 levels had a sixfold greater risk of oncohematological diseases (blood cancers) and an almost 20-fold higher risk of myeloid leukemias (blood and bone marrow cancers). The authors suggested that very high B12 levels could be an early warning sign of hidden blood cancers.

Moreover, attention should be paid to other symptoms such as anemia, unexplained bleeding or bruising, and frequent infections. These symptoms may suggest potential problems with the blood system, and further blood tests or even bone marrow biopsies are recommended to rule out blood-related diseases.

Inflammatory Diseases or Immune Diseases

Chronic inflammation may lead to an increase in B12-binding protein—such as transcobalamin II—as part of the immune response. When these proteins increase, they “carry” more B12 in the blood, which shows up as elevated serum B12 even if the body doesn’t actually need or use all of it.

For example, studies in patients with systemic lupus erythematosus (lupus), an autoimmune disease that causes inflammation throughout the body, have found higher levels of transcobalamin II. This protein may do more than just carry B12—it can also interact with the immune system and make inflammation worse, creating a cycle where inflammation raises B12 levels and the imbalance fuels more inflammation.

In practical terms, if someone has persistently high B12 along with symptoms of inflammation—such as joint pain and swelling, red rashes on the skin, recurrent fevers, or extreme fatigue—this may point to an underlying autoimmune or inflammatory condition. In such cases, doctors usually recommend an immune system work-up, including blood tests for autoimmune markers, to check for diseases like lupus or rheumatoid arthritis.

Malignant Tumors

Certain cancers—including liver, lung, stomach, and breast cancers—can also drive vitamin B12 levels abnormally high. This happens because cancer cells disrupt the body’s normal metabolism. Instead of processing nutrients in a balanced way, tumor cells grow rapidly and stimulate the body to produce more B12-binding proteins (such as haptocorrin and transcobalamin). These proteins then “carry” extra B12 into the bloodstream, which shows up as an elevated B12 level on lab tests.

Studies have found that when plasma B12 levels are persistently elevated (1000ng/mL or higher), the risk of developing solid cancer is six times that of patients with normal B12 levels. On the other hand, nonpersistent B12 elevations are not significantly associated with cancer. This suggests that a sustained elevation—rather than a single abnormal result—should raise red flags.

In this case, special attention should be paid to other symptoms such as unexplained rapid weight loss, persistent pain, long-term fatigue, and a significant decrease in appetite. If these symptoms are accompanied by elevated B12 levels, imaging examinations must be performed to rule out potential tumors.

Precautions With Supplementation

Not only are elevated B12 levels associated with a higher risk of cancer, but excessive B12 supplementation can also be harmful for certain groups of people. Studies have found that men who take more than 55 micrograms of B12 daily double their risk of lung cancer. For male smokers, B12 supplementation also significantly increases cancer risk.

Other studies have found that breast cancer patients who take vitamin B12 supplements during chemotherapy have a worse prognosis, are more likely to relapse, and have a shorter survival period.

Chen Xiaowei, a nutritionist and doctoral student at the Institute of Food Science and Technology at National Taiwan University, emphasized the need for caution: “Any nutritional supplement should be taken in moderation. Excessive intake can put a strain on the body and may even cause other side effects.”

How Much Vitamin B12 Do You Need?

The recommended daily intake for adults is 2.4 micrograms of vitamin B12. Vitamin B12 is a component of nerve membranes and participates in the synthesis of neurotransmitters and DNA, aiding in cell metabolism. It is also essential for the formation of red blood cells. Without enough of it, the body struggles to maintain both brain and blood health.

Vitamin B12 is primarily found in animal foods. Vegetarians can supplement vitamin B12 through fortified foods such as nutritional yeast and plant-based milks (soy, almond, or oat).

Yang emphasized that this guideline is only a baseline: “The recommended intake is an average figure for the general population. People with different health conditions may need more.” He noted that people with mild B12 deficiency may need 50 to 200 micrograms a day for a short period, while severe cases might require 500 to 1,000 micrograms daily under medical supervision.

He cautioned that higher doses should only be used by people with a deficiency and under medical care. For healthy people, taking more than 1,000 micrograms a day long term may be risky. Anyone with nerve, mental health, skin, or blood-related problems should talk with their doctor about the right dosage.