How to tell someone has cancer?

@naya707, these are very general symptoms that could be anything, not necessarily cancer. Please talk to a doctor to find the cause.

No you can't tell by smell. He or she should visit a doctor

The smell could be caused by any number of things, including blood in the stool, which *might* point to colon or stomach cancer (or might not). Like others have said, it's very broad

Are you talking about someone who you believe can't make important decisions for themself due to dementia or some other condition that impairs judgement? There are probably specialists and services you can turn to for guidance and support, especially if you're a caregiver.

No hes my boyfriend we been together for 2 years now and everytime i say something to him about gping to the doctors he says hes fine but ive been watching hes lost alot of weight like very skinny were u can see him bones . He dosent eat much anymore or i make him something cause he says hes hungary but then wont eat , he wakes up with hot flashes, hes can harldy sleep at night cause hes in pain, and always throwing up, and he always saying his that his stomic is hurting, then on top of it he stresses out a lot . He has stints in his heart and has heart attakes and stroks alot . But he keeps telling me hes fine and i know deep in my heart hes not .

I'm so sorry. I don't know what to suggest, but it might be worth reaching out to a social worker for advice. It must be hard for you, worrying about him.

20..0fdsa

It is sometimes i dont sleep at night cause i now know what to look for when hes having a storke or heart attack. So i stay up and keep an eye on him to make sure hes ok. I told him that it would kill me if he just died and didnt tell me he was dying. But what i dont understand is how none of his kids or ex has even notice that hes sick . There spoiled kids and dont relize how lucky they are cause hes rasied all 12 of his kids ive been with him for 2 years and i can see it . I dont know what i should do. No one wants to listen to me .

The usual way to test for cancer in the colon is a colonoscopy. There is a home test
https://pmc.ncbi.nlm.nih.gov/articles/PMC5461150/#:~:text=Polyacrylamid%20hydrogel%20(PAHG%2C%20Bulkamid%E2%84%A2,an%20indication%20for%20female%20SUI. Both require him to see a physician, though.
Naya707, he should see a physician. It might be something that is easy to resolve early on but not so easy later. It might be impossible to convince him.

The first thing my husband noticed, with his stomach cancer, was bad smelling burps. It was because of necrotic (rotting) tissue in his stomach. I would say that a bad or unusual smell should at least be investigated

Without the proper tests, there's no way to say if it's cancer, an ulcer, or something else.

It does sound like he has a lot of denial going on. This can be really hard to overcome. I agree with @northoftheborder about speaking with a social worker. They might be able to give you some tips on getting him to agree to see a doctor.