Take it if your good at writing essays; I know lots of people who have taken Science subjects that are required for Medicine (usually 2 of Biology, Chemistry, Physics, Geography) and taken History as well. It's worth finding out which exam board your school is with and what the course content is on it.
For example, if your studying World War II and Hitler at the moment (a popular choice at GCSE) and your school continues this at AS or A2 you may want/not want to do it again.
It all comes down to your strengths: are you good at writing essays? Being analytical/evaluative? Or are you good at the more "practical" subjects -- are you much better at explaining, doing mathematical calculations? And arguably, most importantly, do you enjoy it?