The International English Language Testing System (IELTS) assesses the English language proficiency of people who want to study or work where English is used as the language of communication. IELTS tests are held in over 900 locations across the world with tests up to four times a month

For Doctors wishing to work in the UK, the requirements are a minimum score of 7, in all  areas of the test (speaking, reading, writing and listening), with an average score across the 4 disciplines of 7.5 . IELTS scores must be less than two years old.

http://www.ielts.org