An alcohol charity has raised concerns about an increased popularity of mixing alcohol and energy drinks.
Drinkaware said there is a "worrying trend" of people making themselves "wide-awake drunk", by mixing the depressant effects of alcohol and stimulatory effects of caffeine.
It said mixing liqueurs and spirits with energy drinks had become "increasingly popular".
Professor Paul Wallace, chief medical adviser at Drinkaware, said: "Mixing alcohol with energy drinks is a popular yet worrying trend.
"Medical research shows mixing caffeinated energy drinks with alcohol is associated with higher levels of alcohol consumption, a likely result of caffeine's stimulating effects increasing the appetite for alcohol.
"It has been shown to lead to a worryingly significant increase in the risk of enduring negative physiological and psychological outcomes, like heart palpitations, agitation, tremors, irritability and tension, compared with drinking sessions without caffeinated drinks.
"The stimulatory effects of caffeine and sedative effects of alcohol are well known, yet people can be mistaken in believing that when drunk together, the two cancel each other out. In fact, caffeine can reduce the sedative effects of acute alcohol consumption, inducing a state sometimes referred to as 'wide-awake drunk'.
"This can put people at risk of injuries because the stimulatory effect of caffeine can lead them to underestimate its impact on their mind and body."