From the Guidelines
Vitamin B12 is crucial for maintaining nerve function, red blood cell formation, DNA synthesis, and brain health, and the recommended daily intake is about 2.4 micrograms for adults, as indicated by the most recent guidelines 1. The goal range for vitamin B12 in blood tests is typically between 200-900 picograms per milliliter (pg/mL), with levels below 200 pg/mL indicating deficiency. This vitamin helps prevent anemia, supports neurological function, and maintains energy levels. Vitamin B12 is naturally found in animal products like meat, fish, eggs, and dairy, making supplementation particularly important for vegetarians and vegans. Deficiency symptoms include fatigue, weakness, constipation, loss of appetite, and neurological changes like numbness and tingling in hands and feet. Some key points to consider:
- The absorption of vitamin B12 involves several steps, including binding to intrinsic factor in the stomach and absorption in the terminal ileum 1.
- Vitamin B12 is a cofactor for two enzymes in humans: methionine synthase and methyl malonyl-CoA mutase, which are essential for mitochondrial metabolism, immune response, and preservation of DNA integrity 1.
- The recommended daily intake of vitamin B12 may vary depending on factors such as age, sex, and health status, with higher amounts recommended for pregnant or breastfeeding women 1.
- Regular monitoring of B12 levels is important for older adults, those with digestive disorders, and people taking certain medications to prevent deficiency 1.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Vitamin B12 is essential to growth, cell reproduction, hematopoiesis, and nucleoprotein and myelin synthesis. The goal of vitamin B12 is to support:
- Growth
- Cell reproduction
- Hematopoiesis (production of blood cells)
- Nucleoprotein and myelin synthesis The goal range for vitamin B12 is not explicitly stated in the provided drug label. 2
From the Research
Vitamin B12 Functions
- Vitamin B12 plays a crucial role in cellular metabolism, particularly in DNA synthesis, methylation, and mitochondrial metabolism 3
- It is essential for hematopoiesis and the development of the brain during childhood, as well as for the metabolism of carbohydrates, fats, and amino acids 4
Vitamin B12 Deficiency
- Vitamin B12 deficiency can cause megaloblastic anemia, neuropsychiatric symptoms, and other clinical manifestations 5
- Subclinical deficiency affects between 2.5% and 26% of the general population, depending on the definition used, and can be caused by inadequate intake, inadequate bioavailability, or malabsorption 3
Diagnostic Biomarkers
- Diagnostic biomarkers for vitamin B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid 3
- Measurement of serum methylmalonic acid can be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12 5
Treatment and Supplementation
- Oral administration of high-dose vitamin B12 (1 to 2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms 5
- Supplementation with a combination of methylcobalamin, adenosylcobalamin, and hydroxocobalamin may be beneficial for individuals with particular single nucleotide polymorphisms affecting B12 assimilation 6