It refers to a process for the preparation of iron (III) hydroxide and activated glucose syrup complexes comprising the following steps: (i) providing an aqueous glucose syrup solution with a dextrose equivalent (DE) of at least 21 and at most 60 as determined by gravimetric analysis at a temperature in the range of 25 ° C to 80 ° C and at a pH in the range of 6 to 13； (ii) add hydrogen peroxide and optionally a catalytic amount of an oxidation catalyst to solution (i),allowing the solution to cool to a temperature between 10 ° C to 45 ° C keeping the solution at this temperature for 5 minutes to 24 hours, obtaining activated glucose syrup； (iii) converting said activated glucose syrup into a complex with iron (III) hydroxide；and (iv) obtain a complex of iron (III) hydroxide and activated glucose syrup wherein the obtained complex has an iron content in the range of 27% to 35% by weight, based on the weight of the complex. It also refers to a pharmaceutical composition. Said complex can be used in iron deficiency therapy in animals and general population.Se refiere a un procedimiento para la preparacion de complejos de hidroxido de hierro (III) y jarabe de glucosa activado que comprende las siguientes etapas: (i) proporcionar una solucion acuosa de jarabe de glucosa con un equivalente de dextrosa (DE) de al menos 21 y como maximo 60 como se determina por analisis gravimetrico a una temperatura en el rango de 25°C a 80°C y a un pH en el rango de 6 a 13； (ii) anadir peroxido de hidrogeno y opcionalmente una cantidad catalitica de un catalizador de oxidacion a la solucion (i), permitiendo que la solucion se enfrie a una temperatura entre 10°C a 45°C manteniendo la solucion a esta temperatura durante 5 minutos a 24 horas, obteniendose el jarabe de glucosa activado； (iii) convertir dicho jarabe de glucosa activado en un complejo con hidroxido de hierro (III)； y (iv) obtener un complejo de hidroxido de hierro (III) y jarabe de glucosa activado en donde el complejo obtenid
