It can come up high for many other reasons, how high was it ? 
if the doctors one comes up as abnormal high then they will probably send you for a colonoscopy to shed some light on it , what concerns made you buy two tests ? 
i am sure it will be nothing but at least you are self aware which is a good thing 

Thankyou for your response, yes I have been told a colonsscopy  is next step,the consultant  said  it wasn't very high but because  a history  of cancer in my family to have one

Thankyou for your response, yes I have been told a colonsscopy  is next step,the consultant  said  it wasn't very high but because  a history  of cancer in my family to have one

yes the earlier they catch it the better, unfortunately bowel cancer can creep up on you with no or very minor symptoms that could easily be passed off as something else but at least you have a colonoscopy, the bowel prep is the worst thing about a colonoscopy the colonoscopy itself is quite straightforward