According to research by TotalJobs , one in five office mugs contains faecal matter because 25 per cent of people don't wash their hands after going to the loo while at work.
The recruitment company enlisted the help of the Hygiene Doctor Dr Lisa Ackerley to get her advice on how to avoid those horrible germs.
She said: "Whatever you do, don't leave mugs or water bottles out overnight. Water is not sterile, and bacteria will build up overnight. Ideally, bring your own mug and bottle to work and don't share them with your colleagues."
And your mug isn't the only disgusting thing in the office.
According to the study the average office desk has up to 400 times more bacteria than a toilet seat.
People who eat at their desks are most at risk of picking up horrible bacteria, followed by people who chew their pens and those who bite their nails.
Dr Ackerley said: "Use a hand gel or antibacterial wipes before eating anything at your desk.
"The best way to avoid contamination though is to take a break and eat elsewhere!"
TotalJobs has offered some more tips on cleaning your mug as clean as possible:
Use your own mug.
Wash up your dedicated work mug in the evening
Leave it on your desk ready for your use only the next day, avoid using shared cupboards where other people can pinch it
Get a mug and bottle for hot drinks on the go, with smooth surfaces so they’re easy to wash
Wash bottles at least once a day because water is not sterile, and bacteria will build up over time. Don’t let anyone else use them.