Vitamin B12 (Active), Folate & Ferritin Blood Test

Ferritin is a protein that stores iron in your body and serves as the most reliable indicator of your total iron reserves. It reflects how much iron is available for producing haemoglobin—the protein in red blood cells that carries oxygen throughout your body. Low ferritin levels indicate depleted iron stores, which can occur before anaemia develops, causing symptoms such as fatigue, weakness, shortness of breath, pale skin, and reduced immune function. Women of reproductive age, pregnant women, vegetarians, vegans, and endurance athletes are at higher risk of iron deficiency. Elevated ferritin can indicate iron overload (haemochromatosis), inflammation, infection, or liver disease—ferritin rises as part of the body's acute phase response. Because ferritin is affected by inflammation, your GP may request additional tests (such as CRP) if your ferritin is unexpectedly high. Results outside the normal range should be discussed with your healthcare provider.

Active vitamin B12, also known as holotranscobalamin, is the biologically available form of vitamin B12 that your cells can actually use. Unlike total B12 tests (which measure both active and inactive forms), active B12 provides a more accurate picture of your true vitamin B12 status. Vitamin B12 plays a crucial role in red blood cell formation, DNA synthesis, and maintaining healthy nerve function. Deficiency can lead to megaloblastic anaemia (where red blood cells become abnormally large), fatigue, weakness, numbness or tingling in the hands and feet, memory problems, and mood changes. People at higher risk of deficiency include vegans, vegetarians, older adults, those with digestive conditions (such as coeliac disease, Crohn's disease, or atrophic gastritis), and people taking certain medications including metformin and proton pump inhibitors. Low levels should be discussed with your GP, who may recommend further testing or supplementation.

Folate (vitamin B9) is an essential water-soluble vitamin that your body cannot produce on its own and must obtain from food or supplements. It is vital for DNA synthesis, cell division, and red blood cell formation. Folate works closely with vitamin B12, and deficiency in either can cause similar symptoms including fatigue, weakness, and megaloblastic anaemia. Folate is particularly important during pregnancy, where adequate levels help prevent neural tube defects such as spina bifida in the developing baby—this is why women planning pregnancy are advised to take folic acid supplements. Good dietary sources include leafy green vegetables, legumes, fortified cereals, and citrus fruits. Low folate levels can result from inadequate dietary intake, malabsorption conditions, certain medications (including some anticonvulsants and methotrexate), or increased requirements during pregnancy. If your folate is low, your GP may recommend dietary changes or supplementation.