Vitamin B12 Blood Test

What is the purpose of this test?

Order this Vitamin B12 Blood Test, which measures the vitamin B12 levels in the blood to help screen for a deficiency. Vitamin B12 is necessary for forming normal red blood cells, nerve function, and tissue and cellular repair. Vitamin B12 is not produced but absorbed into the body after ingesting foods such as: 

• Red meat
• Poultry
• Fish
• Milk
• Eggs
• Fortified products (certain breakfast cereals and bread)

Vitamin deficiencies are primarily caused by malabsorption (when a disease or other condition interferes with absorption) or insufficient dietary intake. However, this is unusual in the United States due to the number of food items enriched with B12. Individuals with a strict diet, for example, those who do not consume animal products, may be more prone to deficiencies. A deficiency can lead to macrocytic anemia (when the body produces fewer but larger red blood cells) and neuropathy (nerve damage causing tingling and numbness in the hands and feet).

What conditions cause abnormal vitamin B12 levels?

Common causes of a vitamin B12 deficiency include:

• Malnourishment
• Liver disease
• Alcoholism
• Celiac Disease
• Cystic Fibrosis
• Inflammatory Bowel Disease
• Hyperthyroidism
• Pregnancy

However, increased vitamin B12 levels are uncommon due to excess vitamin B12 being removed from the urine. However, conditions that can increase B12 level include:

• Liver disease (such as cirrhosis or hepatitis)
• Myeloproliferative disorders (for example, polycythemia vera and chronic myelogenous leukemia)

When should I order a Vitamin B12 Blood Test?

An individual may order a Vitamin B12 Blood Test if their recent CBC with Differential test results detects large red blood cells or if they have experienced symptoms related to a deficiency. Common signs or symptoms of a vitamin B12 deficiency include:

• Dizziness
• Weakness
• Fatigue
• Sore mouth or tongue