My mum is elderly and has been feeling really sick over the past few months and very dizzy. Doctors have done blood tests and trying to get to the bottom of it but recently me and my sister are really concerned. 

she looks extremely emaciated. She also has issues with her bowels 

We feel she needs more thorough investigations with scans but can we insist she has these? She has capacity to make her own decisions but she just goes by the GP and I don’t have much confidence in them. Me and my sister think she has cancer. 

Im going to contact the GP on Monday and express my thoughts but can I insist she is investigated further without frightening her or worrying her? Is there anything else we can do pease we are extremely worried and desperate for help . Thank you