AssalamuAlaikum ...my question is that i see many people smoke eating tobacco and some people have a doubt about a certain disease yet they dont get tested for it if such people die due to cancer or any ither deadly disease is it like suicide as they are risking upon their life is there a sin involved?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is not a sin to not get tested by doctors if someone believes he has a given disease, as it is not incumbent on a person to seek treatment even if he is certain that he suffers from a certain disease. Therefore, he is not to be considered a sinner for abstaining to have his illness diagnosed, let alone considering that to be suicide.

For further information, please refer to Fataawa 119776 and 81345 about the impermissibility of smoking or chewing tobacco and the like.

Allaah Knows best.