From the Guidelines
A normal vitamin B12 level in adults typically ranges from 200 to 900 picograms per milliliter (pg/mL) or 148 to 664 picomoles per liter (pmol/L), depending on the laboratory reference range used. Values below 200 pg/mL are generally considered deficient, while levels between 200-300 pg/mL may be borderline and could still cause symptoms in some individuals. B12 is essential for proper nerve function, DNA synthesis, and red blood cell formation. The body stores B12 in the liver, so deficiency often develops gradually over several years as these stores become depleted. Symptoms of deficiency can include fatigue, weakness, constipation, loss of appetite, weight loss, numbness and tingling in the hands and feet, difficulty maintaining balance, depression, confusion, poor memory, and soreness of the mouth or tongue. Regular testing is particularly important for vegetarians, vegans, older adults, those with gastrointestinal disorders, or people taking certain medications like metformin or proton pump inhibitors, as these groups have higher risk of deficiency 1.
Key Considerations
- The most recent and highest quality study on vitamin B12 levels is from 2020, which provides guidance on the normal range and deficiency treatment 1.
- Vitamin B12 deficiency can be treated with intramuscular injections of hydroxocobalamin, and maintenance treatment is necessary to prevent recurrence 1.
- Oral therapy may be effective in treating vitamin B12 deficiency, but parenteral supplementation remains the reference treatment 1.
Recommendations
- Vitamin B12 levels should be monitored regularly in high-risk groups, such as vegetarians, vegans, older adults, and those with gastrointestinal disorders.
- Treatment of vitamin B12 deficiency should be initiated immediately, and maintenance treatment should be continued for life 1.
- Intramuscular injections of hydroxocobalamin are the recommended treatment for vitamin B12 deficiency, with oral therapy as a potential alternative 1.
From the Research
Definition of Normal B12 Levels
- A normal B12 level is generally considered to be 300 pg/mL or higher 2
- Levels between 200-299 pg/mL are considered borderline 2
- Levels below 200 pg/mL are considered deficient 2
Prevalence of B12 Deficiency
- The prevalence of B12 deficiency ranges between 2.9% and 35% in population studies 2
- In southwestern Colombia, the prevalence of B12 deficiency was 17.8%, borderline was 19.3%, and normal levels was 62.9% 2
- B12 deficiency is more common in individuals with type 2 diabetes, especially those taking high doses of metformin 2