What Does a B12 Test Measure?
The vitamin B12 test measures cobalamin levels in your blood. B12 is essential for nerve function, red blood cell production, and DNA synthesis. Deficiency can cause fatigue, cognitive impairment, numbness/tingling, and a type of anemia called megaloblastic anemia. Your body cannot produce B12 — it must come from animal products or supplements.
How the Test Works
The B12 test is performed via a standard blood draw at any Quest Diagnostics location. Your sample is sent to a CLIA-certified lab for analysis. Results are typically available within 1-2 business days in your JustLabs account.
Conditions It Helps Diagnose
Who Should Get Tested
Vegetarians/vegans, adults over 50, anyone taking metformin or PPIs long-term, people with fatigue or neurological symptoms, and those with a history of gastrointestinal surgery.
Order your B12 test — $8