When should a man get screened for colon cancer if his grandpa died of it in his 40s?

Ten years earlier. While a grandfather is not a first degree relative it may suggest an inherited gene problem and may be a good reason to seek genetic counseling and testing. Most cancers are still random events, but I would suggest doing a colonoscopy at age thirty for peace of mind. If negative, then age forty.
Depends. If neither of your parents had colon caancer or polyps, you are probably not at increased risk based on grandfathers history and can wait til age 50. But if either parent had polyps or cancer consider earlier screening with a colonoscopy. This all assumes your are not having any symptoms now.

Related Questions

I have a family history of colon cancer, grandpa died of it at 42. Should I be concerned?

Perhaps. Colon cancer at a young age may be associated with a familial predisposition. What is the history of other related family members? Typically we would recommend starting colorectal cancer screening earlier in a patient with a family history. Usually 10 years earlier, i.e. 32 in this case. This would certainly be true for your father or mother. Other assoc cancers, include uterine, ovarian, pancreas.
Yes concerned. Yes you have to be concerned, compel you go for early detection and cure. You should have a colonoscopy now follow up as indicated by your doctor and a sure way for cure.

At what age should I start getting tested for colon cancer? My granddad died from it in his 40s.

Consult your MD. The usual recommendation is to have a screening colonoscopy at age 50, but with a stong family history, screening may be started at age 40.
Depends. If your parents have been checked (the one related to the grand parent) for polyps or colon cancer. It is first degree relatives that pose an increased risk for you. So ask you parents if the had a colonoscopy and if they had polyps. If they haven't they need to get one for their sake and yours. If the parent had polyps/cancer take 15 years off the age they were diagnosed for you to start having.

What is the likelyhood of getting cancer if your one grandparent had died in 40s with colon cancer?

General population. If grand parent colon cancer is not genetically related cancer of colon, then incidence will be same as general population.
Unknown. The health history of all of your relatives would be helpful. You should be seen by your doctor and should probably have a colonoscopy before the recommended age of 50 due to your family history. If, after obtaining your family history, you may be recommended to be tested for a hereditary predisposition to colon and other cancers.
Low. While there are a number of genetic syndromes that involve colon cancers, they typically involve 2 or more family members before there is meaningful concern for a genetic syndrome. These can be investigated by blood tests.

I just saw something on tv about a man who died from colon cancer at 29. But I thought this is an old man cancer? Not a young man cancer?

20yo are getting Ca. Younger patients are developing bowel cancer. Part of the problem is that it is viral in origin arising from polyoma virus. This virus has now been seen in several types of vaccines which are utilizing live but maybe only weakened viruses that may enter the host and over several years mutate to possibly initiate problems.