I am a foreign qualified lawyer who has completed the LPC. Should I still take the QLTS?

You can take the Legal Practice Course (LPC) if you are eligible and feel that you wish to, but it is not a mandatory pre-requisite to sitting the QLTS assessments.

You should also note that the LPC is a post-graduate course, and has its own set of educational requirements that must be met in order to be eligible to apply for that course. The costs of the LPC is also substantially higher compared to the QLTS.

Taking the LPC itself does not qualify you as a solicitor. If you go down that route, you will also need to complete a two-year training contract. 

The QLTS does not require this, and on successful completion of the QLTS assessments, you will be eligible to work as a qualified solicitor in England and Wales.