Depending on their breed type and size, your puppy will start adolescence and reach sexual maturity at different times:

Small breeds:

approx. 9–12 months (adolescence from 5 months)

Medium breeds:

approx. 12 months (adolescence from 6 months)

Large breeds:

approx. 12–15 months (below 40 kg) (adolescence from 9 months)

Giant breeds:

up to approx. 24 months (above 40 kg) (adolescence from 12 months)

Although they may start to look like an adult, they are still very much a puppy and they will continue to be for some time, particularly if they are a giant breed, as they won’t reach maturity for at least another year. As an adolescent, they will be energetic and high spirited, and you must provide them with the opportunity to utilize this enthusiasm for life by channeling their energy through training, play and regular exercise.