Adults are being urged to check their pee before they flush to help detect cancer early.
A new campaign by Public Health England is encouraging people who spot blood in their urine, even if it is just once, to visit their doctor.
Blood in wee can be a key symptom of bladder and kidney cancers.
However only 16% of adults aged 50 and over in England check the colour of their urine every time they go the toilet, a survey by PHE found.
This is despite over 50s being most at risk from these cancers.
Women are less likely to check their urine every time, with just 12% of doing so, compared to 20% of men.
Professor Julia Verne, from PHE, said: “It is vital that people know that blood in pee could be a sign of cancer.
“Our research shows only a small number of people check the colour of their pee every time they go to the toilet.
“People need to get into the habit of looking before they flush to spot any signs of blood in their pee.
“And if there is blood, they shouldn’t hesitate about going to their GP. This will help diagnose more people at the early stages, when cancer is more treatable – improving their chances of living longer.”
Blood in urine can vary in colour, from a very diluted pink, to bright red, to dark brown like weak tea, PHE said.
It is a symptom of almost two thirds (64%) of all bladder cancers and around a fifth (18%) of kidney cancers, but blood might not appear every time someone urinates.
However around half (47%) would not get medical help if they saw blood in their urine once and 45% would wait to see if it happened again, the survey of almost 2,500 over 50s in England found.
One in five (20%) said they would not visit a doctor because they would be worried about wasting their GP’s time.
Around 19,100 people are diagnosed with bladder or kidney cancer every year in England, latest figures show, and around 8,000 die from the diseases.
Early diagnosis is crucial, with 84% of those diagnosed with kidney cancer and 77% of those diagnosed with bladder cancer at stage one of the diseases living for at least five years.
The PHE campaign, Be Clear on Cancer, will run until September 23.