Vitamin B12 Test: High Vitamin B12 Blood Levels

Increased B12 Blood Values 

Vitamin B12 Test: High Vitamin B12 Blood Levels

What do extremely high vitamin B12 blood levels mean? Are they harmful? Information, analysis of results and advice on high B12 blood levels.

Vitamin B12 Test and Extremely High Blood Levels

Whilst a vitamin B12 deficiency can be revealed in a B12 test with very low vitamin B12 blood levels, elevated blood levels are also often discovered. Figures above 900 pg/ml are considered high, but certain cases have seen four or even five figure values being recorded. What do these figures mean – and are they cause for concern?

High B12 levels in the blood are not necessarily a reason to panic, as they can stem from a number of different causes. They should however be investigated, as certain severe diseases make up some of the possible causes. Alongside alcoholism, genetic make-up, an impaired B12 absorption and increased transport molecules in the blood, diseases of the liver, kidneys and the blood, such as leukemia, can be considered potential reasons for an increased vitamin B12 blood level.1-4

Reasons for Elevated Vitamin B12 Blood Levels

Increased levels of vitamin B12 in the blood can exist for a number of reasons, which can be divided roughly into the following categories.

  1. The test was simply carried out too soon after the taking of vitamin B12 supplements
  2. The body is failing to use the B12 correctly5
  3. A severe disease is present4,5

This article will look at these causes and their respective next necessary steps in further detail. At the end of the article, there is a precise guide of what to do in the case of elevated blood levels.

Vitamin B12 Blood Test: Think About Timing!

A very common cause of a high B12 blood level is that the blood test is carried out directly after a vitamin B12 injection. This should be avoided and a grace period of 7 – 10 days should be observed, or else the results can be very misleading: the vitamin B12 hasn’t been metabolized yet and the high blood levels are simply a result of the injections. In these cases, high B12 blood levels are absolutely harmless.

Taking high dosage oral supplements can also starkly increase blood levels. In these cases, the same grace period should be observed.

Should high blood levels occur during a course of vitamin B12, then a first measurement to test new B12 blood levels should be taken 10 days after stopping supplementation.

Usage Problems: Deficiency Despite High B12 Blood Levels

If the B12 values are similarly extremely high in a second blood test, the cause can often be difficult to determine. However, most cases fall back to usage problems within the body.

These usage issues occur when the body isn’t capable of properly utilizing vitamin B12, leaving it to accumulate in the blood. It is possible that a B12 deficiency can occur despite the high B12 blood levels; if vitamin B12 isn’t correctly binding to transport molecules and thus is not able to be used by the body, for example.This can be tested using a HoloTC or an MMA urine test, because these tests only measure the usable vitamin B12 (HoloTC) or the metabolic product (MMA test).

Checking B12 Status with an MMA Urine Test

High levels which couldn’t have been caused by a temporary, ill-favored test should always be followed up by an official B12 status check. The most comfortable way of doing this is by measuring the methylmalonic acid in urine, which thus determines how much B12 the cells actually receive. The test can be carried out comfortably and quickly ay home.

High Blood Levels and Vitamin B12 Transport Molecules

Another method which unfortunately involves a trip to the doctor and a blood sample is the HoloTC test, which simply measures the B12 bound to its specific transport molecule, transcobalamin. Only this vitamin B12 is correctly transported to the tissue and body store and thus used by the body.7,8 Unattached vitamin B12 can thus show up in high levels during a serum test, but have no biological function whatsoever.

There are several of these transcobalamin transport molecules, but the so-called transcobalamin II differentiates itself as is makes the vitamin B12 biologically available. The HoloTC test only measures the B12 attached to this transcobalamin II, thus giving a much better indicator of the actual B12 supply being utilized by the body.

Here are the most common usage problems in connection with transport molecules.

Deficiency of Transcobalamin II

Certain rare, hereditary diseases lead to a deficiency of transcobalamin II, meaning that a vitamin B12 deficiency can exist despite a good B12 supply. The B12 serum level in this case shows up very high, despite the fact that a deficiency is present.

Transcobalamin II Antibodies

Hereditary illnesses and long term use of vitamin B12 injections can sometimes lead to the production of antibodies against transcobalamin II, leading to vitamin B12 not being properly used.9

Transcobalamin Bonding Problems

In other cases, transcobalamin is perfectly available but problems exist in the bonding between vitamin B12 and the transport molecule. In this case, there will also be a deficiency despite very high blood levels.

Overproduction of Haptocorrin

Finally, some cases show excessively large production of other molecules which also bond to vitamin B12, most commonly the so-called haptocorrin or cobalophilin, to which transcobalamin I and III also belong. This leads to the available B12 bonding to this molecule instead of to transcobalamin II. Serum values rise here too, even though none of the B12 can be used.

High Vitamin B12 Blood Levels and Diseases

In some cases, the high blood levels can also be attributed to serious diseases. The following mechanisms are responsible for the elevated B12 blood values in these diseases:

  1. Excessive overproduction of haptocorrin
  2. Mistaken excretion of vitamin B12
  3. Release of large quantities of B12 from the body’s B12 storage in the liver
  4. Production of B12 analogs through bacterial overgrowth

Below is a list of the most common diseases that are associated with very high vitamin B12 blood levels.

Cancer and tumors4 
Tumor in the liver

  • hepatocellular carcinoma
    cancer of the liver, primary HCC, HCC10,11
  • Secondary liver tumors 
  • Deficiency in excretion of B12
  • Increased production of transcobalamins
Other Tumors12

  • Breast cancer13
  • Bowel cancer
  • Stomach tumors
  • Pancreatic cancer


  • Elevated production of transcobalamins
Blood Diseases 
Chronic myelogenous leukemia (CML)14Elevated production of granulocytic haptocorrin
Polycythemia vera (PV, Polycythemia, PCV)15,16Increased release of granulocytic haptocorrin
Myelofibrosis (osteomyelofibrosis, OMF, bone marrow fibrosis)Increased production of transcobalamins
Hypereosinophilic syndrome (HES)17Elevated production of haptocorrin
Acute leukemiaIncreased production of haptocorrin
Liver Diseases 
  • Release of vitamin B12 from the body store in the liver
  • Deficiency in production of transcobalamin II
Liver cirrhosisDeficiency in absorption of vitamin B12 by the liver
Alcoholic liver disease19,20
  • Deficiency in production of transcobalamin II
  • Overproduction of transcobalamin I und II
Kidney Diseases 
Kidney failure21Deficiency in excretion of vitamin B12 and consequent accumulation in the blood
Intestinal Diseases
Bacterial overgrowth in the bowel22,23Increased production of B12 analogs through bacteria

High Vitamin B12 Levels in Chronic Inflammations

Certain cases of high vitamin B12 blood levels can be linked to autoimmune diseases with chronic inflammations. The mechanism here is difficult to determine, however it is assumed that it stems from an increased production of transcobalamin II.22-24 The prevalence and significance of these observations are however presently unclear.

Increased B12 levels here seem to occur much less frequently than in the previously mentioned diseases, so this relationship seems to play a relatively subordinate role, as far as current research shows.

What Should I do if I Have High Vitamin B12 Blood Levels?

High vitamin B12 blood levels should always be examined further, in order to rule out any serious diseases. Often, if high vitamin B12 blood levels are confirmed, it can be a simple failure in measurement, resulting from the period of time between taking supplements and undergoing a blood test – certainly no cause for panic.

Even experienced general practitioners are sometimes stumped when interpreting high B12 blood values, so here is a little guide on the steps to follow after a high B12 blood level shows up.

Guide to High B12 Blood Levels

Vitamin b12 Hohe Blutwerte


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