Dr Hajo Auwerda is a haematologist with a special interest in vitamin B12. He is known in the Netherlands as the B12 expert. He has written dozens of scientific publications in leading medical journals and is a sought-after speaker at international medical conferences. From this position he has built up an (inter) national network of doctors, clinical chemists and nutritionists who all have many years of experience in conducting research into the consequences of B12 deficiency. He now uses these contacts and partnerships at B12 Clinic where, in addition to patient care, clinically relevant research is being conducted to attain a clear medical consensus and adequate tests to speed up diagnosis and therefore treatment. From all over the country and abroad, GPs and specialists refer their patients to him.