When you take a job with a company, your employer agrees to compensate you for the time and labor that you offered them. The work that you do may be critical to the ability of a company to function.
For example, if you work on a production line, your unique skills are probably important to turning out the appropriate number of components or finished products that the company needs to produce each day if they hope to turn a profit.
When you find yourself in a situation where you need to take time off of work for your health or a serious family situation, your employer might resent your absence. However, provided that the length of your employment and the company size qualify you for unpaid leave under the Family and Medical Leave Act (FMLA), your employer cannot penalize you for taking an appropriate leave of absence.

When can a worker potentially take FMLA leave?

Generally speaking, your employer will have to have at least 50 employees within a 75-mile radius of the location where you work in order for the FMLA to apply to their business. Additionally, you will personally have had to work 1,250 hours in the last 12 months and have been employed with the company for at least 12 months.
If you meet those criteria, then in certain circumstances, you have the right to FMLA leave. The circumstances that qualify someone for FMLA leave include the birth of a child, the foster placement or adoption of a child, illness or injury on the part of the employee, and medical conditions in immediate family members such as parents, children or spouses that require care from the worker.
If your employment situation and your family circumstances meet these requirements, your employer should allow you to take up to 12 weeks of unpaid leave. If you need to care for your family member and they are a military service member, you may be able to take up to 26 weeks of leave without career consequences.

How employers punish workers who asked for FMLA leave

There are a number of ways that your employer might illegally retaliate against you for making an appropriate and legal request for unpaid leave. Often, employers will simply deny such requests and then discipline or fire an employee who calls in sick or otherwise does not show up to perform their job.
Other times, the company might allow the leave but then make work more difficult for that person when they return. For example, your employer might try to demote you or cut your wages. They might assign you to a different, more difficult job. They might also openly harass you and make jokes about your lack of work ethic because you put your family or health before the company.
If your employer has retaliated against you for seeking FMLA leave or if they have denied a reasonable leave request, you may need to speak with a lawyer to explore what options you have.