Vitamin B12 (Serum or Plasma Concentration)

Why This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands or feet. It could also be done to check for vitamin deficiencies, especially if you have conditions like pernicious anemia, celiac disease, or long-term vegan/vegetarian diets. Additionally, it may be part of routine screening for people at higher risk, such as older adults or those with certain gastrointestinal disorders.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it involves a blood draw. If you’re taking certain medications (like certain B vitamins or antacids), let your doctor know beforehand.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed to measure the concentration of vitamin B12. The results help determine if your levels are within a healthy range or if further evaluation is needed.

What the Results Mean

Low vitamin B12 levels may indicate a deficiency, which can affect how your body uses energy and produces red blood cells. High levels are less common but may require investigation to rule out other conditions. Your doctor will interpret the results in the context of your symptoms and medical history.