Taking sick leave for two weeks would put 91% of front line workers under financial pressure, while 28% would have to choose between heating and eating.
Almost all (92%) are worried about burning out if they have to work through illness.
More on sick pay:
Under current statutory sick pay (SSP) employees earn £109.40 per week if they are too ill to work, from the fourth day of absence.
The UK is one of the only OECD nations where employers are the sole funders of sick pay for up to 28 weeks, according to Rob Moore, director of insurance at Wagestream.
For example, Icelandic employees can receive a minimum of two days of sick leave for every month they work.
They receive 100% of their salary for time off because of an illness, some of which may come from an employer or the government's Social Insurance Administration.
Speaking to HR magazine, Moore said: “In most high-income countries, the duration covered by the employer is just 5-15 days before benefits come into play.
“This discrepancy needs to be addressed, with the government stepping in with more funding support - much like the current conversations taking place around issues like childcare.”
The study found 45% of employees are unsure what their sick pay entitlement is.
Moore said employers need to improve support and signposting around sick pay and leave.
He said: “Until the government implements reforms, employers should consider how else they can help. Many are unaware of their entitlements, highlighting an awareness issue which sits with the employer to address.
“Similarly, employers themselves need to understand the financial difficulties which sickness absence can cause for their people.
"This understanding is particularly important before entering into conversations with benefits providers about the additional support available, and will help employers to implement the best option for their workforce."
A separate study from the Trades Union Congress found SSP fell by 1.25% in real terms between 2010 and 2019.
In 2019 sick pay was worth 18% of average earnings – compared with 34% when it was first introduced in 1983.