Overview
Vitamin B12 is essential for red blood cells and normal nervous-system function. A deficiency develops gradually and causes anaemia and neurological symptoms.
Why it's done
It is ordered for fatigue, numbness in the limbs, memory problems, a vegetarian diet or gastrointestinal conditions.
How to prepare
Light fasting is preferable; tell your doctor if you take B12 supplements.
What to expect
A venous blood draw.
Understanding the results
A low level indicates deficiency; folate and ferritin tests are added when needed. Treatment (supplements or injections) is carried out under medical supervision.