Study Warns Against Excessive Caffeine Before Driving

A recent study has raised concerns about the impact of excessive caffeine consumption on driving performance. Conducted by Censuswide for Carmoola’s “Curbing The Caffeine” campaign, the research surveyed 2,000 residents of the U.K. aged 16 and older. It revealed that approximately 11 million drivers in the U.K. exceed the recommended daily caffeine limits, potentially compromising road safety.

The study collaborated with Dr. Tim Mercer, a general practitioner at TJ & SE Mercer Healthcare Ltd. According to their findings, moderate caffeine intake, defined as up to 300 mg per day, can enhance alertness. However, surpassing this amount can lead to adverse effects. Dr. Mercer noted, “While the NHS advises that 400 mg of caffeine per day is a safe upper limit for most healthy adults, exceeding these levels can lead to restlessness, palpitations, and anxiety.”

For drivers, maintaining calmness and control is crucial. “Too much caffeine can cause jitteriness and even urinary urgency, both of which can be distracting behind the wheel, where your full attention should be on the road,” Mercer emphasized.

The survey revealed that nearly half of respondents aged 17 to 24 reported experiencing caffeine-related side effects while driving. Notably, 16 percent of this age group reported these effects frequently. Furthermore, men were found to be twice as likely as women to notice these side effects, with 11 percent of men acknowledging issues compared to just 5 percent of women.

Among all drivers surveyed, 5 percent admitted they could not drive properly without caffeine. This figure increased to 9 percent among those aged 25 to 34. Dr. Mercer cautioned against over-reliance on caffeine, stating, “Caffeine can make you feel more alert, but over-reliance can lead to dependency and withdrawal.” He recommended staying hydrated, eating regularly, and considering decaffeinated coffee for a mental boost without the negative side effects.

Comparative Caffeine Levels and Driving Risks

Carmoola has released a guide detailing caffeine levels in popular beverages, using sources such as BBC Good Food and Monster Energy to standardize caffeine content per milliliter for easier comparison. They referenced Costa Coffee’s sizing chart, the U.K.’s leading coffee chain in 2025, which shows that a large cappuccino contains 400 mg of caffeine.

Supporting these findings, a 2020 study from Loughborough University examined the caffeine consumption patterns of over 3,000 truck drivers. Participants were divided into two groups: high-caffeine consumers, who averaged 7.5 caffeinated beverages per day, and low-caffeine consumers, who had about one daily. The results indicated that drivers in the high-caffeine group were involved in more accidents and reported poorer overall health compared to their lower-caffeine counterparts.

The study highlighted that high-caffeine participants were more likely to engage in risky behaviors, such as smoking and drinking alcohol, while also exercising less and having unhealthier diets. They experienced increased daytime sleepiness and reported feeling more fatigued overall.

In summary, while caffeine can provide a temporary boost in alertness, moderation is key, especially for those behind the wheel. As the research illustrates, excessive caffeine intake can lead to distractions that could jeopardize road safety.