There has seen a rise in visits to sexual health clinics from people having unprotected sex while under the influence of drugs and alcohol, according to a doctor in north Wales.
Dr Ushan Andrady warned that people should consider the risks before engaging in such behaviour.
The health board which covers the region has launched a campaign to increase sexual health awareness.
It comes after a fivefold increase in syphilis cases in south west Wales.
Sexual health and HIV consultant Dr Andrady, the clinical lead for Betsi Cadwaladr University Health Board's 'Sextember' campaign, said people were not aware of the risks of having unprotected sex whilst under the influence of drugs and alcohol.
"We have definitely seen a rise in people coming into the clinic after having sex whilst under the influence of drugs and alcohol, and they regret what they have done," he said.
"Sometimes people forget about protection when they are under the influence of drugs and alcohol."
In 2016, a report by the British Medical Journal highlighted the association between substance misuse and higher risk of sexual behaviour.
Analysis based on a study of more than 15,000 men and women revealed that among 16-24 year olds, more than 40% of women reported to have had unprotected sex after binge drinking compared to 31% of men in the same age group.
Dr Andrady said people should make sure they were prepared for every possibility.
"Have a game plan; carry condoms or plan your contraception because sometimes sex just happens and is unplanned," he said.
"Also, know your limits with alcohol, make sure that both you and your partner have not had too much to drink.
"Make sure that both of you can consent to having sex, you have the right to say no at any time.
"And don't panic; know where to access emergency contraception and sexual health services."