Vitamin B12

What Is Vitamin B12?

Vitamin B12, or cobalamin, is an essential nutrient (meaning that the body does not produce it endogenously) that performs an array of physiological roles in the body – including, among others, protecting nerve function, aiding in DNA and red blood cell production, and promoting healthy cell metabolism, among others. B12 occurs in four forms with slight alterations to their chemical composition:

• Hydroxocobalamin
• Methylcobalamin
• Adenosylcobalamin
• Cyanocobalamin (Cyanocobalamin is the synthetic form of B12 that is produced pharmacologically for administration to patients with diagnosed B12 deficiencies.)

Most populations in the developed world, including Americans, typically get enough B12 through diet alone, without the need for supplementation. The common sources of dietary B12 include:

• Fish
• Chicken
• Red meat
• Dairy
• Eggs

Pernicious Anemia and B12 Deficiency

In addition to serving the nervous system, B12 is also crucial for red blood cell production. As such, a failure of the intestines to fully absorb B12 through food, called "pernicious anemia," can precipitate a dangerous drop in red blood cell production. According to research, pernicious anemia is a rare condition, occurring in only about 0.1% of the population. However, the condition accounts for as high as 50% of the total B12 deficiencies seen in US patients.

Pernicious anemia presents a danger to affected patients' health that must be caught early. A B12 test can detect insufficient levels of the vitamin and, in turn, provide the diagnostic guidance needed to correct the issue before red blood cell counts drop further.

Why Order a B12 Blood Test?

It is common to order a B12 blood test if low or excessive levels of the vitamin are suspected. Often, because B12 is used to synthesize the coating of nerve cells called the myelin sheath and to aid in nerve repair, sub-optimal B12 levels can cause a number of symptoms associated with impaired function of the peripheral nervous system such as:

• Balance problems
• Paresthesia (tingling in the extremities, often called "pins and needles")
• Weakness in the limbs
• Cognitive issues and/or dementia
• Pale skin
• Neuropathy

Several demographics are at a higher risk than the general population of developing B12 deficiency. Accordingly, these groups should perform regular tests to ascertain current levels of the vitamin:

• Vegans
• Strict vegetarians
• Diabetics
• Patients who have received gastric bypass surgery
• Older adults

There is some evidence that pregnant women may benefit from B12 because the vitamin may help prevent Spina Bifida.

Because vitamin B12 is sourced through animal products in the diet, vegans are at particularly high risk of developing a B12 deficiency. As such, if you are a vegan, you should seriously consider performing regular blood screenings to survey your body's supply of this crucial nutrient. When test results indicate sub-optimal levels of B12, you may want to add high-quality B12 dietary supplements to your daily routine to augment your intake through diet.

Individuals with gastrointestinal conditions are also at higher risk of developing B12 deficiency. Due to the inability to absorb B12 through the intestines in instances of pernicious anemia, patients with gastrointestinal issues are also prime candidates for B12 screening. These include patients with:

• Crohn's disease
• Celiac disease
• Atrophic gastritis

Patients taking certain medications may be at greater risk of B12 deficiency as well. Several medications have been shown to sometimes reduce B12 levels in patients who take them. Examples of these medications include:

• H2 receptor blockers (i.e., Pepcid and Zantac)
• Metformin
• Proton pump inhibitors (i.e., Prilosec, Prevacid, Nexium)

Additional Lab Tests To Consider With A B12 Blood Test

In addition to blood tests for circulating B12, a healthcare provider may also order a methylmalonic acid (MMA) and homocysteine (HC). Both MMA and homocysteine levels are known to increase due to a b12 deficiency. While some patients with a b12 deficiency show normal levels of b12 in the blood, their MMA and HC levels may be elevated.

Interpreting B12 Test Results

Without medical training, accurately interpreting B12 test results can be difficult for a pair of important reasons:

• Normal levels of B12 vary from patient to patient, depending on age, gender, and other factors. Therefore, what are adequate B12 levels for some patients may not be adequate for others; there is no universal standard.
• Several underlying conditions, and/or medications intended to treat them, may affect B12 levels in some patients. These factors must be weighed when analyzing test results.

Importantly, the B12 blood test only determines the extent of a deficiency or surplus of the vitamin – not the underlying cause.
For these reasons, it's critical to consult with a professional medical provider who can take the totality of your individual circumstances into account when assessing the results of the B12 test.

Generally speaking, though, there are rough guidelines to determine whether B12 levels are normal or abnormal.

General Guidelines for Interpreting B12 Test Results (picograms/milliliter)

<150 pg/mL: Low

200-600 pg/mL: Normal

>800 pg/mL: High

Again, professional guidance is needed to effectively analyze individual test results on a case-by-case basis.

What Causes Low B12 Test Results?

The causes of low B12 levels, some of which we have explored already, vary widely, possibly including:

• Inadequate dietary intake of B12 (as seen in vegans)
• Gastrointestinal issues, such as pernicious anemia, that interfere with B12 absorption
• Gastrectomy
• Autoimmune disease
• Use of medications that prevent B12 absorption

If insufficient B12 levels are discovered, corrective action to reverse the deficiency, usually through B12 supplementation, is recommended. A comprehensive medical screening may be necessary for patients who test low for B12 to determine the root cause of the issue. Again, B12 and folic acid deficiency often occur simultaneously due to pernicious anemia and other medical conditions that cause malabsorption of these B nutrients.

What Causes High B12 Test Results?

We've discussed extensively the causes and symptoms associated with low levels of B12, but what about test results that indicate elevated B12 levels? Individuals with high body mass indexes (BMIs) or those who consume large amounts of meat are at the highest risk of having dangerously elevated B12 levels. Additionally, high B12 concentrations are often the result of chronic conditions such as:

• Renal (kidney) failure
• Diabetes
• Leukemia (bone cancer)
• Liver disease

If your test results indicate high levels of vitamin b-12, you should discuss them with your healthcare professional to investigate the source of the surplus.

Where Can I Get a B12 Blood Test Near Me?

Visit Health Testing Center's Lab Locator to find a convenient testing location nearby. If you have questions, contact Health Testing Centers for additional information. We will provide the lab with the correct CPT code when needed.

A Note on COVID and Lab Tests

Due to the COVID pandemic, most medical labs have instituted strict social distancing guidelines and mask-wearing guidelines. Please be prepared and plan accordingly. If you wish not to visit a local lab, we offer an extensive selection of test kits for your at home clinical chemistry testing needs.

References:

Nutrients Medical Journal. "Vegan Diet, Subnormal Vitamin B-12 Status and Cardiovascular Health." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4145307/
CNS Neuroscience and Therapeutics. "B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6930825/
Frontiers in Pharmacology. "Vitamin B12 Enhances Nerve Repair and Improves Functional Recovery After Traumatic Brain Injury by Inhibiting ER Stress-Induced Neuron Injury." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6491933/
Medical and Dental Research Association (MDRA) "The metabolic processes of folic acid and Vitamin B12 deficiency." http://www.jhrr.org/article.asp?issn=2394-2010;year=2014;volume=1;issue=...
Journal of Blood Medicine.
"Optimal management of pernicious anemia." https://pubmed.ncbi.nlm.nih.gov/23028239/
Public Library of Science.
"Methylmalonic Acid and Homocysteine as Indicators of Vitamin B-12 Deficiency in Cancer." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4725715/

Reviewed By: Dr. Kurt Kloss, MD
Last Reviewed Date: Jul 02, 2021