Vitamin B12 & Folate Test

About this test

This panel measures both vitamin B12 and folate (vitamin B9) together, because these two B vitamins work closely together in many of the same pathways — particularly in producing healthy red blood cells and maintaining the nervous system. Deficiency in either (or both) causes a distinctive type of anemia called megaloblastic anemia, characterized by abnormally large red blood cells that don't function properly.

Testing both together is more informative than testing either alone, because the symptoms of B12 and folate deficiency overlap significantly, and because high folate intake can mask a B12 deficiency while nerve damage continues to progress — making it important to measure both.

Components

• Vitamin B12 (Cobalamin): Required for nerve health, red blood cell production, and DNA synthesis. Deficiency causes fatigue, weakness, tingling or numbness in the extremities, memory problems, and anemia. Most common in people who eat no or little animal products, older adults, people with malabsorption conditions (celiac, Crohn's, pernicious anemia), and those taking metformin long-term.
• Folate (Vitamin B9): Essential for cell division, DNA repair, and red blood cell production. Folate deficiency also causes megaloblastic anemia and is particularly critical before and during pregnancy to prevent neural tube defects. Folate is found in leafy greens, legumes, and fortified foods, but absorption can be impaired by alcohol use, certain medications, and GI conditions.

Who is this test for?

This combined test is most relevant for anyone being evaluated for macrocytic anemia (abnormally large red blood cells), neurological symptoms such as numbness or balance problems, or unexplained fatigue. It is also commonly recommended before and during pregnancy, for older adults, and for people following plant-based diets. Both B12 and folate work together in critical cellular processes, so measuring them together provides a more complete picture.