Most of us know the calculation. You’re rough, you’ve got things on, and it’s not “bad enough” to call in. So you go in - a bit grey, a box of tissues under your arm, hoping nobody notices. It’s practically a British tradition.

But new research suggests this instinct to push through may be doing more damage than you realise - not just to how quickly you recover, but to how likely you are to end up off sick later in the year.

Britain has a presenteeism problem.

Working while unwell - a behaviour researchers call “presenteeism” - is remarkably common in the UK. According to analysis by the Institute for Public Policy Research (IPPR), UK workers are among the least likely in the OECD to take sick days, but among the most likely to come in while ill.

On average, British employees lose the equivalent of 44 days’ productivity a year to presenteeism - up from 35 days in 2018. The IPPR calculates that the hidden cost of employee sickness has risen by £30 billion since 2018, with £25 billion of that down to presenteeism rather than actual sick days taken.

Flu is a significant part of this picture. Research by RAND, published in a peer-reviewed journal, estimates that approximately 2.4 million UK working adults fall ill with influenza each year, resulting in around 4.8 million working days lost to absences and reduced productivity.

The seasonal economic cost runs to roughly £644 million - or about £272 for every worker who gets sick. And that figure only captures the direct losses. It doesn’t account for what happens to workers who show up unwell, spread it to colleagues, and delay their own recovery.

What the new research found

A longitudinal study published in BMC Public Health in March 2025 tracked 4,180 wage workers in South Korea from 2019 to 2022, drawing on nationally representative data from the Korean Health Panel Study. The researchers set out to examine whether working while sick - presenteeism - predicted higher rates of later absence due to illness.

The findings were clear. Workers who reported presenteeism earlier in the study period had around 30% higher odds of being absent due to illness at a later point, compared with those who didn’t report working while ill.

Employees who had previously taken sick leave showed an even stronger pattern - they were nearly 3.5 times as likely to be absent again in the following survey period. Crucially, when the researchers tested the relationship in both directions, they found that presenteeism predicted later absenteeism, but absenteeism did not predict future presenteeism. The signal ran one way.

Why flu is a particularly poor illness to work through

A UKHSA study of working adults in England during February and March 2024 found that around one in six had worked while sick with a respiratory infection - and that those doing so estimated they were operating at roughly three-quarters of their usual capacity.

Flu is an especially problematic illness to power through. It is infectious before symptoms fully develop, meaning workers can spread it at the office before they even feel ill enough to consider staying home. The NHS advises people with flu symptoms to rest at home, and the HSE guidance to employers is unambiguous: send staff with symptoms home quickly. Working through flu not only risks infecting colleagues but can extend recovery time.

Why UK workers keep coming in sick

The IPPR identifies several reasons UK workers are reluctant to take sick days: poor workplace culture, financial insecurity, limited access to sick pay, and a sense of not wanting to let colleagues down.

Research by Bluecrest Wellness involving 1,400 UK workers found that 77% had worked while sick in the previous 12 months, with one in five saying they felt pressure from their employer to do so.

Interestingly, those with the lowest income, least formal qualifications, and those in minority ethnic groups are disproportionately affected - the people who can least afford the loss of a day’s pay are often those most likely to work through illness.

What this means in practice

The study’s authors make a point worth sitting with: a 30% increase in risk, applied across a large workforce, “may translate into substantial cumulative costs related to productivity loss, healthcare utilisation, and workforce sustainability.” In plain terms - the short-term cost of taking a day off sick is usually much smaller than the long-term cost of pushing through, getting worse, and eventually missing several days at once. Or of starting a chain reaction of illness through your team.

For employers, the researchers suggest that presenteeism - unlike a prior history of illness or a chronic condition - is something that can actually be addressed. Paid sick leave policies, more supportive management cultures, and lighter workloads during recovery are all practical levers.

For workers, the key takeaway is simpler: if you’re genuinely unwell, especially with flu or another respiratory infection, rest tends to be the better investment - for you, and for the people around you.