This year’s flu season is shaping up to be a bad one and workers should take note of when it is time to call in sick.

According to the Center for Disease Control Guidelines, people should stay home for 24 hours after running a fever, but many workers don’t heed this advice and often to go into the still sick because they don’t want to lose a pay day or waste hard-earned vacation or sick leave. The Center for American Progress reports 38% of employees in the private sector workers don’t have one paid sick day—making it tough choice to stay at home in bed to recover.  

Experts warn that ignoring an illness or returning to work too early can end up costing workers more in the long run.  “If you go to work you could get sicker because you are at work not healing,” says Trisha Torrey, About.com Guide to Patient Empowerment. “It can cost you more than a lost day of pay.”

Here’s a look at three reasons why employees should call in sick.

Going to Work Sick Can Cost More  

In a perfect world, employer would pay you for sick days, but that often doesn’t happen. This especially holds true for hourly workers, who come in sick over fear of having their pay docked. Working while still sick will make it harder for the body to recover and could lead to more intense illness that could keep a worker out of commission for a long time and racking up big doctor bills.

“It causes more damage if they do go to work,” says Torrey. “If they get sicker it will cost even more because they will lose more time or lose more money.” 

Employers Don’t Want Sick Workers

While a company doesn’t want healthy employees calling out sick, it also doesn’t want sick workers showing up and infecting co-workers. If enough people get sick it can impact the ability to run a department or an organization which is going to cost the company money, says Paul McDonald, senior executive director of staffing company Robert Half International.

Recently companies have been encouraging sick workers to stay home or, if they are up to it, to work from home to avoid contagion. “Many companies have a sickness plan in place,” says McDonald, noting the responsible companies are encouraging and rewarding those employees who make the right decision not to come to work when they are sick.

Risking Social Consternation

No one wants to sit next to the person coughing all over the place, or sharing a conference table with someone constantly blowing their nose.

According to the Centers for Disease Control, people with some or all of the following symptoms: fever, cough, sore throat, runny nose, body aches, headache or chills may have the flu and should stay home to avoid spreading it around the office. The CDC also recommends people stay home for at least 24 hours after a fever breaks. “We’ve all gone to work and someone is coughing up a lung and touching the coffee pot and we’re thinking how are we going to protect ourselves,” says Torrey. “You can alienate your co-workers if you come to work sick.”