[Vitamin B9 and B12 : clinical manifestations, screening and substitution].

Deficiency in vitamins B9 and B12 are common in general practice, due to their high prevalence in the population, especially among elderly patients. This article will present the clinical manifestations of vitamin B9 and B12 deficiencies, which can sometimes be insidious. We will discuss screening strategies, which are based on the presence of compatible symptoms as well as risk factors for deficiency. The choice of administration route for substitution depends both on severity and etiology; but the oral route has demonstrated similar effectiveness compared to intramuscular administration.