How old was Darren shan when he was blooded?

Darren Shan, the vampire in "the saga of Darren shan" did eventually drink blood. After avoiding it for months and leaving himself on the brink of death he finally drank from his dying friend Sam Grest, in order to absorb some of his soul and, in a way, keep him alive. From that point on he drank on a regular basis, taking a small amount from each person but never killing them.