Vitamin B12, in Visit Clinic

Vitamin B12 supports red blood cell production and DNA synthesis, maintains healthy nerve cells and myelin, and aids energy metabolism by helping convert food into usable energy. It also helps regulate homocysteine levels, supporting cardiovascular and cognitive health, and is important in pregnancy for fetal brain and nervous system development. Deficiency can cause anemia, fatigue, memory problems, and neuropathy.

Vitamin B12 deficiency commonly causes fatigue, weakness, pale skin and shortness of breath. Neurological signs include numbness, tingling, balance problems and coordination difficulties. Cognitive and mood changes — memory loss, confusion, depression — can occur. Other features include a sore, smooth tongue, mouth ulcers, jaundice and a fast heartbeat. Symptoms may develop slowly and worsen without treatment.

Clams are the richest natural food source of vitamin B12, supplying far more B12 per serving than most other foods. Other excellent sources include beef liver, oily fish (mackerel, sardines, salmon), shellfish (oysters, mussels), fortified cereals, dairy and eggs. Vegetarians and vegans should use fortified foods or supplements to reliably meet B12 needs.

Typical adult serum vitamin B12 reference range is about 200–900 pg/mL (≈148–665 pmol/L). Levels below ~200 pg/mL are commonly considered deficient; 200–300 pg/mL can be borderline and may prompt further testing (e.g., methylmalonic acid) or clinical assessment. Lab reference intervals vary, so interpret results alongside symptoms, local lab ranges, and patient age.

Vitamin B12 deficiency is mainly caused by inadequate dietary intake (strict vegan diets), impaired absorption from pernicious anemia (loss of intrinsic factor), prior gastric surgery or atrophic gastritis, gastrointestinal disorders (celiac disease, Crohn’s, bacterial overgrowth), certain medications (metformin, proton‑pump inhibitors), and age‑related decreased absorption; chronic alcoholism and intestinal parasites can also contribute.

Yes — daily vitamin B12 is safe for most people and often recommended for vegans, older adults, and those with absorption issues. The adult recommended intake is about 2.4 µg; many supplements deliver much higher doses (e.g., 500–1,000 µg), which are typically well tolerated because B12 has low toxicity. Consult your clinician if you have kidney disease, take metformin/PPIs, or suspect deficiency to choose dose and form.