Younger people with bowel cancer symptoms may make 10 or more visits to a GP before finally being diagnosed due to age bias, experts say.

People aged 25 to 44 are more likely to be diagnosed with the deadly disease at later stages as GPs often have a low suspicion of cancer when they are presented with symptoms in young people.

A study led by Klay Lamprell from Macquarie University's Australian Institute of Health Innovation found this often leads to missed diagnostic opportunities, which can affect patient outcomes.

"People with early onset bowel cancer take longer to get diagnosed than older people, about 60 per cent longer," Dr Lamprell told AAP.

Even when younger patients have blood in their poo or rectal bleeding, GPs may not immediately refer them to specialists for further testing which means they may be overlooked for the disease.

"When bowel cancer is identified early amongst most people, there's a very high survival rate so it's alarming to think that delays are being caused in the healthcare pathways," Dr Lamprell said.

Being diagnosed at a later stage can increase the likelihood of aggressive treatment and affect fertility and ostomy management.

The study published in the BMJ Open medical journal also found younger people may spend between three months and five years seeing multiple doctors before diagnosis.

Bowel cancer is the deadliest cancer in people aged 25 to 44.

Incidence rates of the disease in people aged 15 to 24 years have nearly tripled in the past three decades.

The research was conducted in collaboration with charity Bowel Cancer Australia.