How long does a PHD take if you already have a masters?

I gained my first and second (masters) degree in the UK. I then moved to Canada and found work as a biomedical scientist. Im interested in teaching in the future and advancing to higher echelons but generally just curious and would like to do a Phd in biochem in a few years. As I already have a masters, would i still be required to take those 1 or 2 years masters of a phd?