“My B12 blood test is normal, I don’t need any vitamin B12”.
“My vitamin B12 lab test is above normal, I don’t need any more B12”.
Each time I hear someone say this I quietly flinch, wondering if they are yet another medically misinformed individual suffering from a potentially serious B12 deficiency. Like many lab tests (see Thyroid newsletter), the standard blood test for vitamin B12 is subject to serious error, especially when B12 lab test results show normal to above normal results.
Here is a case from PubMed.gov (US National Library Medicine National Institute of Health) that exemplifies my concerns. A 59 year old woman with progressively worsening heart palpitations, severe fatigue and difficulty breathing for about one month, was admitted to the hospital. Her diet was good and the only medication she was taking was thyroxine for her hypothyroid condition.
Blood tests on multiple occasions showed her B12 levels were normal to high normal. This woman underwent numerous, comprehensive and invasive testing, including bone marrow biopsy, and conditions such as acute leukemia were ruled out. Ultimately she was given a series of B12 shots and within one month she was fine. In conclusion, the author of this study stated that “normal levels [of B12 in the blood] do not rule out the presence of vitamin B12 deficiency, leading to a high risk of clinical error”.
A quick search of Pub Med reveals several studies showing B12 test results do not correlate with the symptomatic B12 status of an individual. In other words, the blood tests are unreliable, especially when they indicate normal or above normal levels of vitamin B12.
Vitamin B12 deficiency should be suspected in the elderly, if unexplained neurologic problems, if experiencing gastrointestinal problems including low stomach acid which may show with difficulty digesting animal protein, after gastrointestinal surgery, if consuming a vegan diet, or experiencing unexplained fatigue and insomnia. For more on this subject and B12 deficiency risks please see my website newsletter on vitamin B12.
There are several reasons why vitamin B12 blood tests are unreliable and the chemistry of this is complex. One issue is due to the fact that vitamin B12 levels fluctuate over time. Another issue is that B12 blood tests do not necessarily reflect the status of B12 presence at the cellular level, such as in the nervous system where deficiency can cause severe and life threatening neurologic problems.
B12 test results can be artificially elevated due to the presence of food metabolites called inactive B12 analogues. These are particles that look like B12 to the test apparatus, however they are not truly B12, thus creating false and misleading normal or elevated B12 test results. Some food items that may falsely elevate blood levels of B12 include spirulina, nori, sourdough bread, kombu, barley malt syrup, tempeh and fish. These inactive B12 analogues can actually inhibit the metabolic activity of true B12 further complicating the health picture.
Vegan diets which lack vitamin B12 are high in the B12 analogue look-alike B12 molecules. Because of this, these individuals will get a false elevation on B12 blood tests and unwittingly suffer from multiple B12 deficiency symptoms.
The reason that doctors still run this test is as complicated as the test itself. As a rule, medical doctors have no nutritional training and the B12 blood test is a nutritional status test. It is based on how the body functions. MD’s are focused more on emergency medicine, and ND’s more focused on functional medicine which is what this test is about.
In summary, while all blood tests are subject to some degree of error, the standard B12 blood test is likely the most unreliable of all lab tests. Due to false readings of normal or elevated B12 status, B12 blood test results can seriously misdirect and harm people who are desperately in need of B12 augmentation. The moral of this newsletter is not to rely on B12 blood test results to guide in health care. If in doubt, one should enhance their dietary or supplemental source(s) of B12, and if health improvement is noted, consider an on-going B12 support program.
I hope you have enjoyed this newsletter. Comments and feedback are welcome.
Jon Dunn, ND