Half of people with possible cancer symptoms in the UK don't contact their doctor for at least six months, which could reduce their chances of survival.
A survey by Cancer Research UK found that poorer people are less likely to see their family doctor once they seek help.
Less than half of people who have a red flag cancer symptom contact their doctor within six months.
According to Cancer Research UK, waiting so long could mean doctors miss the chance to diagnose the disease early, which can have dire effects on the patient's health.
The chief executive of the Patients Association said that as a nation we are not very good at seeking help when we notice something is not right.
The findings may help to explain why the UK has a worse record than most other countries.
75% of cancer cases will be detected at stage one or two when they are more likely to be treated, thanks to the efforts of the National Health Service. It is introducing new blood tests to spot the disease, using innovative means to enable quicker identification of lung cancer, as well as running public awareness campaigns urging people to act when they see a symptom.
The results of the survey were weighted to be representative of the UK population. Of those who had a possible symptom of cancer, 1,230 had a red flag symptom, which included coughing up blood, a new or unusual lump and changes to the appearance of a mole.

There are tens of thousands of patients waiting for treatment in England.
Only half of the 1,230 people contacted their GP practice after they developed a possible cancer symptom. Less than half of those with red flag symptoms did so. The proportion of people in social groups who got an appointment was higher than those in C2DE.
Only half of C2DEs went back to their GP when they continued to show symptoms.
The gap in accessing services between the UK's most and least deprived groups is worrying, according to CRUK's chief executive.
Our daily newsletter is sent out every weekday at 7am.
It is not easy talking about cancer, but a conversation with your doctor could save a life. It's important to get a cancer diagnosis early in order to get the best possible treatment.
Anyone who is concerned that they may have a symptom of cancer should seek help.