Human resources departments must carefully balance the needs of employees, managers, and the entire company. As a result, while they are often a place of support and help for employees, they are also full of professionals who must think pragmatically about the best interests of their employer.

Before you share a secret about yourself or your career with your HR department, think about how it will be perceived by your employer. In many workplaces, there are ten things that you should never share with HR.

10 Things You Should Never Share With HR

1. Illegal activity. Even if the illegal activity takes place outside work you should never mention it at work. Some, such as recreational drug use, may go against written company policy regardless of how often or where you do it. And others may compel human resources to report you to the police.

2. Potentially not coming back from leave. When you're home with a new baby, taking care of an elderly relative, or on medical leave, it's natural to consider whether not going back for work is the best choice for your life balance. But if you tell human resources, your employer could end up uncertain of your reliability or commitment.

Even if you can't legally be fired while on leave, you could still be moved into another department or gives less prestigious work when you do come back. To prevent your career from stalling, don't talk to HR until you've made a decision.

3. Invented reasons for taking leave. Whether you're pretending to go to a relative's funeral or claiming you have a sick child at home, inventing reasons to take extended leave can make it easier to handle HR. But lies and excuses can come back to haunt you, especially if you end up needing time off for genuine reasons in the future.

In most cases, if your employer discovers that you lied, termination is an automatic consequence.

4. Lies during the hiring process. Yahoo CEO Scott Thompson, who left his job in 2012 after only four months, falsely claimed on his resume to have a degree in computer science﻿﻿. He was forced to step down as CEO. Most companies have a policy that any untruthful statement on your job application can result in termination after you are hired.

5. Potential changes in your partner's career. If you know that a change in your partner's career will require you to reduce your hours, job hunt, or move to a new city, you should talk to your employer as soon as possible. But until those changes are certain, don't bring it up.

Your organization is not going to promote you or provide you with career development opportunities when they think that you will leave. You may also find yourself ineligible for benefits like educational assistance, which employees often repay through years worked.

6. Moonlighting or working a second job. If you are employed full time and tell human resources that you are working a second job, you communicate that you might not be fully committed to the company and your current job. Your employer may also blame any failings you exhibit such as delayed work, arriving late, or being unavailable for a meeting on your second job.

7. Lawsuits for harassment, ADA accommodation, or civil rights violations. If you filed a lawsuit against a previous employer, it's best not to mention it to your new one. Even ethical HR departments live in fear of lawsuits. And EEOC lawsuits take up time and energy, along with exposing years of employee record keeping to the government and lawyers.

If you share information about previous lawsuits with your new HR department, they are likely to look at you with suspicion or consider you a threat. If you're job searching, employers do discriminate (secretly, as it's illegal) when they know that you have sued employers in the past.

8. Potential time off or disability for medical issues. If you share information about medical concerns before they begin affecting your work, you may box yourself out of transfers, promotions, opportunities, and team leadership positions. Your employer may begin to work around you to protect their productivity and profitability.

If you do need to take time off, you should absolutely discuss that with HR, but wait until it's no longer theoretical.

9. Charges of DWI, DUI, tax evasion, fraud, or theft. Sharing criminal charges that have been brought against you will make you appear untrustworthy. Unless an event threatens to flow over into your workplace—in which case, always tell HR before they are blindsided—your personal business is private.

The exceptions are if you receive a DUI and drive a company vehicle for business or if your employer does employee background checks. If you're applying for a job, if you have a felony on your record, reveal it when asked on the application. If the employer finds out in a background check, you won't get the job.

10. Problems in your personal life. Stories about your failed relationships, a lawsuit against your neighbor, or family troubles don’t belong at work. They can consciously or unconsciously affect your career and opportunities, creating a bias against you or making you seem unreliable or difficult.

If something threatens to flow over into the workplace, such as an ex who shows up at the office or work events to harass you, this should be shared with HR. Otherwise, don’t give your employer any more information than is necessary for a team-oriented workplace.

When to Talk to HR

Human resources doesn't just look out for the interests of your employer. The department's job is the balance the needs of the company while ensuring that employees receive the protections and information they need.

If you know for certain that changes in your personal life will impact your work, talk to HR. They can help you understand what your options are and create a plan that works for both you and your employer. But in general, no matter how friendly you are with human resources employees, it's best to keep your personal life away from the HR department.