Vitamin B12

Serum vitamin B12 (cobalamin) measurement screening for deficiency that causes neurological damage, macrocytic anaemia, and cognitive impairment. At EUR 28.36 under GOAe 1.0x rates. Particularly important for vegetarians, vegans, older adults, and patients on metformin or proton pump inhibitors -- all groups at elevated risk of B12 depletion.

Vitamin B12 (cobalamin) is an essential water-soluble vitamin required for DNA synthesis, red blood cell production, myelin maintenance, and one-carbon metabolism. The body stores 2-5 mg of B12, primarily in the liver, and daily losses are approximately 1-3 micrograms. Because stores are substantial relative to daily requirements, clinical deficiency typically takes 3-5 years to develop after intake ceases, but subclinical depletion begins much earlier. Serum B12 below 200 pg/mL (148 pmol/L) is considered deficient, and 200-300 pg/mL is a grey zone where functional deficiency may already be present. Functional markers -- methylmalonic acid and homocysteine -- are more sensitive than serum B12 alone but are not included in this single-analyte test. If serum B12 falls in the grey zone and clinical suspicion is high, follow-up with holotranscobalamin (active B12) or methylmalonic acid is recommended. B12 deficiency causes megaloblastic anaemia (macrocytic red blood cells due to impaired DNA synthesis) and, more insidiously, peripheral neuropathy, subacute combined degeneration of the spinal cord, cognitive decline, and psychiatric manifestations including depression and psychosis. Neurological damage can become irreversible if deficiency is prolonged. Risk groups include strict vegans (B12 is found almost exclusively in animal products), vegetarians with low dairy and egg intake, adults over 60 (20-30% have reduced gastric acid production and impaired B12 absorption), patients on metformin (which reduces B12 absorption by 10-30%), and patients on long-term proton pump inhibitors (which suppress the gastric acid needed to release B12 from food proteins). The GOAe 1.0x price is EUR 28.36 -- B12 assay at EUR 16.76 plus EUR 4.20 blood draw and EUR 7.40 outpatient fee. No fasting is required. Results are typically available within 1-2 business days.