Why should be antibiotics only taken by an advance of a qualified doctor?

This is a very good question. Most of the infections are viral infections and they do not need any antibiotic. Secondly most of the bacterial infections are mild and they also do not need antibiotic. Thirdly the dose, duration and selection of antibiotic needs a wise judgement. Which you can not decide. Forth reason is injudiciuos use of antibiotic can lead to emergence of antibiotics resistant bacteria. As you have in case of ndm 1 or superbug in your hand. This generation is responsible to the welfare of the coming generations. So in short the antibiotics should not be taken without the prescription of the qualified doctor.