Serum or plasma concentration of vitamin B12 (substance 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 and feet. It could also be done if you have a history of poor diet, certain medical conditions (like pernicious anemia or celiac disease), or if you’re taking medications that interfere with vitamin B12 absorption.

What to Expect Before the Test

You’ll likely have a simple blood draw from a vein in your arm. No special preparation is needed unless your doctor instructs otherwise. If you’re on certain medications (like metformin), let your lab know beforehand.

What the Results Mean

Low levels may indicate vitamin B12 deficiency, which can affect how your body uses energy and produces red blood cells. High levels alone don’t usually cause concern unless related to other conditions.

Common Conditions Linked to Results

Low vitamin B12 can cause anemia, nerve damage, or cognitive issues. High levels might suggest overabsorption or certain genetic disorders, but further testing is often needed.