How many times have you gone in to work when you're really not up to it?
It's called presenteeism and it's on the rise.
A study by health insurer Vitality has found that more than 40% of employees said their work was being affected by health problems - a figure that's risen by a third over the last five years.
It found that people are putting aside both mental and physical health problems to attend work.
And in its recent annual Health and Well-Being at Work Survey Report the Chartered Institute of Personnel and Development (CIPD) also found evidence of unhealthy trends in the workplace.
The CIPD said more than four-fifths (83%) of its respondents had observed presenteeism in their organisation, and a quarter (25%) said the problem had got worse since the previous year.
Sarah Mitchell-Hume didn't know anything about mental health when she had a panic attack at her desk.
She was two years into her career in engineering recruitment, a job she absolutely loved, when she suddenly became unwell. Sarah was diagnosed with depression.
"I felt pressurised to go back to work, even though I was signed off sick," she recalls.
"I was physically present but mentally I wasn't doing anything. And I'd just zone out, there was nothing going on behind my eyes. I think I just cleared my inbox every day. It made me more ill. I should've been at home recovering."
Aged 24, she was just starting her career when she felt like it had come to an end.
If you break a leg, it's clear you need time off. Having a mental illness or suffering from workplace stress can be harder to spot. But Vitality's research has shown that these are the biggest factors behind the growing problem of people turning up for work when they're not fit enough to do their jobs.
Vitality runs an annual survey, Britain's Healthiest Workplace, involving 167 organisations and 32,000 staff. The aim is to understand and tackle poor health and wellbeing across the UK workforce.
Presenteeism is a clear and accelerating trend. It's just one of a number of studies which have come to the same conclusion.
It's obvious that if we're not at our best, then we're less productive employees.
When Dale Garbacki lost his wife in 2014, he hit rock bottom. He was her main carer as well as trying to hold down a full time job in technical support for Dixons Carphone.
"Productivity dropped to what I call bare minimums," he now admits.
"I'd had several warnings. By finally reaching out to the company and having a private chat with one of my managers, about how I was feeling and what I was going through at home, the loss of my wife, he said 'ah, why didn't you tell me sooner. We'll need to get you some help'."
Whilst Ms Mitchell-Hume felt she had no support in her workplace and ultimately left her job, Mr Garbacki started a work sponsored fitness programme to help him turn things around.
He runs before work in his local park in Preston as well as working out in the company gym.
"I'm definitely a lot better than I was. Overall I feel better in myself. I have more positive and confident feelings and I actually look forward to each day."
He has now earned his first ever full bonus.
'Good business sense'
His employer has been on a journey, too.
Dixons Carphone's Head of Corporate Social Responsibility, Kesah Trowell, had her work cut out trying to persuade her company to sponsor one of the UK's biggest long distance treks or runs, the Race to the Stones.
It proved a huge success with its workers who took part, kick starting a raft of other wellbeing initiatives including Mr Garbacki's bootcamp programme.
"It really does make good business sense," says Ms Trowell.
"It's important that we have happy, healthy and engaged workforce, particularly since we're in a retail environment. "
She adds: "Technology makes it easy for people to hide behind their desks, their computers or their phones. It's easier for more presenteeism than there would've been a few years ago. That's why it's important for us to manage this."
Could reducing presenteeism help solve the UK's chronic productivity puzzle?
"Absolutely," says Vitality's chief executive Neville Koopowitz.
Productivity is the main driver of long-term economic growth and living standards. But our workers aren't anything like as efficient as they should be.
"Workplace stress and mental wellbeing has a massive impact. We believe presenteeism is the key issue to Britain's productivity problem, where people are at work and not performing in an optimal way," Mr Koopowitz says.
Ms Mitchell-Hume does freelance and voluntary work now as well as being a busy mother. She's happy but she just wishes her employer had handled things differently.
"It was so incredibly difficult. A bit of compassion, empathy and flexibility would've made all the difference," she says.
"The workplace can be a tough place to be. There's so much more to be done to look after employees."