The company has therefore urged employers to ensure any staff who they suspect may have Long COVID to get the right support.
The illness can cause a range of changing neurological, psychiatric and physical symptoms of which there are now over 50 reported.
Examples include breathlessness, muscle or joint pain, headaches, fatigue, digestive issues, anxiety and vertigo.
To further complicate matters, individual symptoms can improve and relapse, causing some people to feel that they are suddenly unable to cope.
Christine Husbands, managing director for RedArc, said it is vital people get the right support as early as possible or symptoms could be more prolonged.
She told HR magazine: “One of the main issues with Long COVID is that the goalposts keep shifting, employees can feel quite in control on one day and then a change in the type or severity of symptoms can mean a huge step backwards on another.
“This has huge implications for treatment and support, and employees need to be treated as individuals as the symptoms vary so much from person to person.”
Husbands said a one-size-fits-all approach can not address the very personal nature of the illness, and that support needs to be agile and adapt to the individual’s condition as it evolves.
In February this year, the Office for National Statistics found more than a million people in the UK were experiencing Long COVID symptoms.
An estimated 674,000 people said their symptoms have negatively affected their ability to undertake their day-to-day activities.
Husbands said the illness’s impact on people’s work lives could drastically affect their mental health.
What does Long COVID in the workplace look like?
She said: “Over many years of supporting people with physical illnesses, we’ve witnessed individuals struggle mentally when they are not able to live their lives as fully as they once could, particularly when there is no real end date in sight.
“In addition, in terms of COVID-19 and Long COVID, we’re not only dealing with the mental health impact of the condition itself but also the fact that people have been coping in isolation or with very little social contact which can exacerbate the impact on mental health.”
Husbands explained generic employer support will not be effective for Long COVID as symptoms vary widely among sufferers.
“It is important support is personalised and people with specific symptoms are offered advice on pacing, rehabilitation and support in returning to the workplace.
“By utilising the support available in employer-sponsored health and wellbeing benefits, insurances and via membership organisations, those with long COVID will get the best possible help in dealing with the after-effects of the virus,” she said.