You will not be able to go on a medicine course straight from a BTEC. As others have said if your A levels haven't gone to plan then you may struggle with a medicine degree. Have you looked at general biology/bio medicine degrees? You would be able to do a BTEC and get on one of those courses. I know some universities let you transfer to medicine after the first year of a general biology degree. However it will likely be very competitive and you will need top grades in order to transfer. Some people also choose to study medicine after they have got a biology degree first, but again it is likely that you will need a first or a 2.1 to even be considered. My advice to you would be to do a BTEC in applied science and work out exactly what it is you like, there are so many different biological degrees you just need to find the one you like.