Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a significant role in several bodily processes. It is involved in the formation of healthy red blood cells, DNA synthesis, and the normal function and development of nerve cells. A deficiency occurs when the body does not get enough or cannot absorb sufficient amounts of this vitamin. Recognizing and diagnosing this condition is important due to its wide-ranging effects on physical and neurological health.
Understanding the Symptoms
A deficiency in vitamin B12 can manifest through a variety of symptoms affecting different body systems, often developing gradually. Neurological symptoms commonly include numbness or tingling sensations, vision problems, difficulty remembering, confusion, or challenges with walking and balance. Hematological symptoms frequently arise because vitamin B12 is needed for red blood cell production. These can include extreme tiredness, weakness, lack of energy, shortness of breath, pale or yellowish skin, and a rapid heartbeat. General symptoms like a sore, red tongue (glossitis), mouth ulcers, decreased appetite, and unexplained weight loss can occur.
Initial Blood Tests
When a vitamin B12 deficiency is suspected, the initial step in diagnosis typically involves a blood test to measure serum vitamin B12 levels. This test determines the amount of vitamin B12 circulating in the bloodstream. A simple blood draw is performed, and the sample is then sent to a laboratory for analysis. The primary purpose of this test is to identify if levels are lower than normal, which serves as a first indicator of a potential deficiency.
Often, a complete blood count (CBC) is performed concurrently with the serum B12 test. The CBC provides information about various components of the blood, including red blood cells. In cases of vitamin B12 deficiency, the red blood cells may appear larger than normal, a condition known as macrocytosis. This finding on a CBC can further support a suspected B12 deficiency.
Decoding Test Results
Interpreting serum vitamin B12 test results involves understanding the typical numerical ranges, which can vary slightly between laboratories. Generally, a normal range for serum vitamin B12 is considered to be between 200 to 900 picograms per milliliter (pg/mL). Levels below 200 pg/mL are typically considered deficient.
A borderline range, usually between 200 and 300 pg/mL, might prompt further investigation. It is recognized that some individuals can experience symptoms of deficiency even when their B12 levels fall within the lower end of the normal range or are considered borderline. A diagnosis of vitamin B12 deficiency is not solely based on a single numerical result. It involves a comprehensive assessment that combines the measured vitamin B12 levels with a careful evaluation of a person’s physical and neurological symptoms.
Advanced Diagnostic Steps
When initial serum vitamin B12 levels are borderline, or if symptoms are present despite seemingly normal B12 levels, additional tests can provide more definitive answers. Methylmalonic acid (MMA) and homocysteine tests are often used to confirm a functional vitamin B12 deficiency at a cellular level. When vitamin B12 is insufficient, these substances accumulate, leading to elevated levels in the blood. An elevated MMA level is considered a sensitive indicator of vitamin B12 status, and an MMA level greater than 0.271 micromol/L suggests a deficiency.
Homocysteine levels also rise as vitamin B12 status declines, with values higher than 15 micromol/L suggesting a deficiency. However, MMA levels can also be elevated in kidney disease, and homocysteine can be influenced by other factors, such as low folate levels. To identify the underlying cause of a confirmed deficiency, particularly if pernicious anemia is suspected, intrinsic factor antibody tests may be performed. Intrinsic factor is a protein needed for vitamin B12 absorption in the small intestine. The presence of intrinsic factor antibodies suggests an autoimmune condition where the body attacks this protein, preventing B12 absorption.