From the Guidelines
The normal level of vitamin B12 in blood is typically considered to be above 150 pmol/L, as levels below this threshold may indicate vitamin B12 deficiency, according to the World Health Organization (WHO) 1.
Definition of Normal Levels
The WHO defines vitamin B12 deficiency as serum vitamin B12 < 150 pmol/L (< 203 ng/L) 1. It's essential to note that a higher level does not exclude vitamin B12 deficiency, and in such cases, blood methylmalonic acid must be assayed to confirm the diagnosis.
Key Points to Consider
- The normal range for vitamin B12 can vary depending on the laboratory reference range used.
- Values below the defined threshold are generally considered deficient.
- Certain populations are at higher risk for B12 deficiency, including older adults, vegetarians and vegans, individuals with gastrointestinal disorders, and those taking specific medications.
- Supplementation may be recommended if deficiency is detected, and the method of supplementation can vary depending on the severity and underlying cause of the deficiency.
Importance of Accurate Diagnosis
Accurate diagnosis of vitamin B12 deficiency is crucial, as it can have significant implications for morbidity, mortality, and quality of life. Therefore, it's essential to rely on the most recent and highest-quality evidence, such as the WHO recommendations 1, when determining the normal level of vitamin B12 in blood.
From the Research
Normal Level of B12 in Blood
- The normal level of vitamin B12 in blood is not explicitly stated in the provided studies 2, 3, 4, 5, 6.
- However, the studies discuss the importance of vitamin B12 in cellular metabolism, DNA synthesis, and methylation, and the consequences of its deficiency 3, 4.
- The diagnosis of vitamin B12 deficiency is based on laboratory tests, including serum vitamin B12 level, methylmalonic acid, and homocysteine levels 2, 3, 5.
- The studies also discuss the various causes of vitamin B12 deficiency, including inadequate intake, malabsorption, and impaired cellular uptake or metabolism 3, 4, 5.
- Treatment of vitamin B12 deficiency typically involves supplementation, either orally or parenterally, and the choice of treatment depends on the severity of the deficiency and the patient's overall health 2, 3, 4, 6.
Laboratory Tests for Vitamin B12 Deficiency
- Serum vitamin B12 level is the most commonly used test for diagnosing vitamin B12 deficiency 5.
- Other tests, such as methylmalonic acid and homocysteine levels, can also be used to confirm the diagnosis 2, 3, 5.
- The lack of a robust absorption test and the compromised sensitivity and specificity of other tests can make it difficult to determine the cause of depleted vitamin B12 status 5.