Health authorities are worried that the safe sex message has fallen off the radar in WA, with new figures showing a spike in people diagnosed with HIV.

The WA Health Department says the annual number of HIV notifications has doubled in a decade, including a 16 per cent increase last year.

Though AIDS groups say the increase is likely to reflect more people being tested, the department says it is worried that some people are complacent about unprotected sex.

WA's sexual health and blood-borne virus program manager Lisa Bastian said the number of new HIV cases had grown from 51 in 2004 to 139 last year.

She said the numbers were particularly alarming for men who have sex with men, with a 27 per cent increase in HIV reports in this group last year.

"In 2014, there were 75 HIV notifications among men who have sex with men, which is double the number notified in 2009 and the highest annual number reported in WA since 1991," Ms Bastian said.

"While part of this increase can be explained by increased HIV testing and better targeted testing in high-risk groups, it is likely that an increase in unprotected sex is also part of the story.

"Safe sex and regular testing are the best protection against HIV and other sexually transmitted infections and it's important to drive this message home to everyone who is sexually active."

The average age of HIV cases last year was 37 and slightly older in men compared with women.

Ms Bastian said the department was working with the WA AIDS Council to increase awareness of the need for safe sex and HIV testing in the gay community.

GPs were also being provided with information to improve testing for sexually transmitted infections, including HIV.

Council chief executive Andrew Burry said though the increase in HIV cases had to be recognised, he believed it was largely attributable to more people being tested.

"We've wanted to see a rise in notifications because over the last four years we've been asking gay men to test much more regularly and they have responded to that and have been tested in significantly higher numbers," he said.

"So, in some ways I would have been alarmed if after all the investment that's been made we hadn't seen that increase, which is really the only measure for success for a testing strategy."