Vitamin B12

What is Vitamin B12 (Cobalamin)?

Vitamin B12 is a water-soluble vitamin that is involved in the metabolism of all human cells. B12 is an essential vitamin, meaning that it must be obtained from the diet.  Deficiency can result in cognitive and mental problems, dizziness and numbness, and - if left untreated - permanent neurological damage. 

Vitamin B12 deficiency is quite common.  Estimates suggest that up to 20% of the elderly population may be deficient or depleted in Vitamin B12 (1). Pregnant women and young children, vegetarians, vegans, and patients with intestinal problems or those taking stomach acid suppressants are all at increased risk of B12 deficiency.

Taking a serum vitamin B12 test may not be enough to determine B12 sufficiency.  In case of doubt, an MMA test can help to confirm B12 status.


Why Test Vitamin B12?

Unless this is ordered as a retest or for a specific reason, we recommend ordering this as part of a health test.

Symptoms related to B12 deficiency include mood swings, hand/feet numbness, ‘brain fog’, fatigue, headaches, depression, anemia, infertility, insomnia, irritability and anxiety.

Risk Factors
Vegans, vegetarians and those who eat no or little meat/seafood or have celiac/intestinal disease.

Health History
You have a history of low B12, or other reasons that suggest you may have low B12.

You take a drug, such as hydrocortisone or antacids, that increases the need for B12.

What do the results mean?

Normal serum B12 levels may indicate sufficiency and suggest that symptoms are likely due to another cause.  However, if symptoms are present and persist, a methylmalonic acid (MMA) test may be needed to complete the picture. This is especially true if B12 is in the lower half of the reference range. 

What causes low vitamin B12?

The level of vitamin B12 circulating in your bloodstream is lower than expected. A low B12 and/or folate level, especially accompanied by signs and symptoms, indicates vitamin B12 deficiency. The extent of the anemia or associated neuropathy cannot be detected on a serum B12 test. A level within the reference range does not necessarily indicate optimal levels and cannot rule out deficiency.

The serum vitamin B12 test is limited in specificity and sensitivity and misses many people within the ‘grey zone’ of deficiency. Therefore, those with signs and symptoms of vitamin B12 deficiency should follow-up with a homocysteine test, and possibly an MMA test, in order to better determine vitamin B12 status. This is particularly true if the result is within the lower half of the reference range. but even higher serum vitamin B12 levels do not indicate that vitamin B12 is being properly utilized at the cellular level.

This is when an MMA test may be helpful (the MMA test measures cellular levels). Causes of vitamin B deficiency include diets low in B12 (such as vegan diets), pregnancy and breastfeeding, malabsorption, celiac disease, pernicious anemia, and gastric bypass surgery.

Several health conditions can cause vitamin B deficiency, including pernicious anemia, (the most common cause), celiac disease, inflammatory bowel disease (IBD) such as ulcerative colitis or Crohn’s’ disease, small intestinal bacterial overgrowth (SIBO), intestinal parasites, such as tapeworms, hypochlorhydria (reduced stomach acid production). B12 can also be lowered by medications including aspirin, metformin, and birth control pills.

Deficiency is common with:

  • Unsupplemented vegan diet
  • Long-term use of antacids or H2 proton pump inhibitors
  • Surgery to remove parts of the stomach, such as gastric bypass, or the intestines
  • Pancreatic Insufficiency
  • Heavy drinking or chronic alcoholism
  • Medication use (e.g. metformin, omeprazole, methotrexate, and medications to prevent seizures) 

What causes high
vitamin B12?

High vitamin B12 levels are very often caused by excessive supplementation. High levels of B12 are not very common and are not usually monitored. However, elevated B12 levels can be indicative of a health condition.

More information

High levels of folic acid supplements can mask B12 deficiency. Please tell us if you are taking folic acid supplements.


No advance preparation is needed for this test.  Remember to take I.D. with you when going to take a test.


© 2024 Nordic Wellth AB Terms Of Use