Typically, family and medical leave-taking is full-time, meaning that workers will stop working for a set period of days or weeks. However, less commonly, leave-taking may involve a reduction of work hours without a complete cessation of employment [4]. Types of leave-taking in the United States most commonly include medical or personal disability leave, caregiver leave, and parental or pregnancy leave [4]. All three of these types of leave are provided for at the federal level by the FMLA [4]. The most common form of leave-taking is medical or personal disability leave, accounting for slightly more than 50% of all worker leave-taking in the United States [5]. Caregiver and parental or pregnancy leave combined account for the remainder (slightly less than 50%) of U.S. family and medical leave-taking [5].

Medical leave is sometimes conflated with workers' compensation programs, for the understandable reason that both involve time off of work for a health or medical reason [6]. However, separate laws, rules, and resources affect workers' compensation programs, and as such, family and medical leave policy and programs are generally treated as distinct from workers' compensation, encompassing forms of medical leave that are either not related to on-the-job injuries or that may be available after workers' compensation benefits expire [6]. It is particularly helpful for medical and social service providers to understand this distinction, as workers who use workers' compensation benefits until they expire may return to work before medically advisable in the event that options for medical leave-taking are not fully explored. Although, in practice, leave-taking may also overlap with other forms of time off of work, including vacation time and short-term use of sick days or personal days, under law and policy, family and medical leave-taking are usually treated as somewhat distinct from each of these other practices as well [6].

Typically, family and medical leave-taking is full-time, meaning that workers will stop working for a set period of days or weeks. However, less commonly, leave-taking may involve a reduction of work hours without a complete cessation of employment [4]. Types of leave-taking in the United States most commonly include medical or personal disability leave, caregiver leave, and parental or pregnancy leave [4]. All three of these types of leave are provided for at the federal level by the FMLA [4]. The most common form of leave-taking is medical or personal disability leave, accounting for slightly more than 50% of all worker leave-taking in the United States [5]. Caregiver and parental or pregnancy leave combined account for the remainder (slightly less than 50%) of U.S. family and medical leave-taking [5].

Some U.S. states enable leave-taking for additional reasons, and the FMLA has similarly been interpreted using an expanded scope. For instance, domestic violence leave-taking is a more recent development and enables workers who are victims of domestic violence, or related forms of assault in some states, to take leave while recovering from abuse, while engaged in legal processes such as obtaining a restraining order, or to facilitate safety, for instance when a victim of violence needs to temporarily relocate to another home or shelter not located near a place of employment [7].

Medical/health documentation is almost always a vital element of leave access. For personal medical or disability leave, it is typically not necessary to specify that a worker is completely incapacitated (unless this is true). The general threshold for leave eligibility is that the worker is temporarily either unable to work at all or cannot do so without substantial threat to health or safety. If it would be physically conceivable that a worker could show up to work and attempt to perform but doing so would substantially exacerbate an illness or injury, this is sufficient for the purposes of establishing that a person cannot reasonably work.

In practical terms, documentation that indicates only that leave-taking is in a patient's or client's "best medical interest" might be insufficient, but language indicating "medical necessity" or specifying that leave is mandatory for the purposes of restoring health, functionality, and/or employability will serve the purpose of documenting medical eligibility. Providers who exaggerate or distort the need for leave-taking with the intention of ensuring eligibility may inadvertently harm their clients or patients in addition to potentially committing a breach of medical ethics. For instance, if a provider were to indicate that a condition is so severe that a patient might never be able to recover in any respect, this documentation might actually trigger loss of employment, because the basic premise of leave-taking is that there is at least a substantial prospect of return-to-work. When the likelihood of return-to-work is uncertain, it is best to avoid speculation and simply present the need for leave based on the estimated time the worker will likely require, up to the maximum available. In essence, documentation should be accurate and clearly stated (to the extent possible, allowing for medical terminology), should emphasize medical necessity, and should not prematurely indicate that absence from work is certain or extremely likely to be permanent.

For caregiver leave, healthcare or social service providers also play a role in providing required documentation for employers and/or government agencies and in counseling family members of ill or injured persons about their options to secure leave. Providers should keep in mind that, as with other areas, there can be different rules for states or municipalities, as compared to the federal FMLA. In simple terms, a "caregiver" is a person who needs to leave employment for a period of time in order to address the health- or disability-related needs of a family member [22]. Providers will generally need to document that the person who is the proposed recipient of care has a serious or substantial illness or injury, such that access to a caregiver is medically necessary [22].

Certain categories of workers will not be covered under any instrument. For example, undocumented workers—defined as those who are not authorized to work legally in the United States—will usually not be protected by any area of family and medical leave law (although a Wisconsin court ruled that undocumented workers are eligible for leave under the FMLA, without back pay) [27]. New hires and temporary workers who are employed through an employment agency generally do not qualify for family and medical leave rights unless they can establish consistent employment with a particular employer for a substantial period of time or unless the temporary employment agency meets the requirements for an eligible employer [25].

Data on family and medical leave utilization indicate certain demographic differences in leave-taking patterns. Not unsurprisingly, female workers are more likely than their male counterparts to take parental leave during a period of pregnancy and to take parental leave for a longer period of time [37]. Female workers are also substantially more likely to take caregiver leave than male workers [38]. Male workers primarily utilize personal disability leave, with caregiver and parental leave accounting for a relatively minor portion of the leave-taking behavior of employed men [39].

Leave-taking is a finite resource. While the duration of leave and the benefits available may vary based on the state, employer type, and localized policy, it is virtually always true that workers have only a certain amount of leave time available. Female workers spend disproportionately more leave time on caregiving for others and during pregnancy, and therefore tend to have proportionately less available access to leave for other personal disability or health issues [40]. As a consequence, there are gender disparities in medical leave utilization. While the full contours of these disparities are not yet manifest in empirical research, initial study supports the supposition that reduced medical leave access has corresponding negative health consequences stratified by gender [31].

Wage disparities and differences in leave-taking norms partially account for racial-, gender-, and disability-based disparities in leave utilization among those workers who are otherwise legally eligible to benefit from family and medical leave rights and resources. The social and health benefits of leave-taking access are stratified at a more basic level, however, as legal eligibility for leave is also substantially affected by dynamics of racial, gender, and disability inequity and by access to the benefits of citizenship. The categories of workers least likely to enjoy leave eligibility—underemployed and temporary workers, migrant agricultural labor, and immigrant workers without the legal right to work in the United States—are disproportionately drawn from vulnerable communities of color [45]. Women and people with disabilities are also disproportionately likely to be underemployed, working sporadically, part-time, or based on temporary contracts, and therefore are comparatively less likely to be leave-eligible [46]. Women (and in some contexts, teenage girls), primarily from African American and Latina communities, make up the vast majority of "pink collar" or domestic workers, employed as maids, nannies, or related forms of domestic service. These spheres are almost never organized to enable leave eligibility and are often entirely informal [47].

Workers in these spheres often develop disabilities or chronic health problems, not based on any pre-existing condition, but because the conditions of work are frequently exploitative, physically unsafe, or exhausting and do not reliably generate enough income to support basic needs and enable health and well-being [48]. The conditions of work, coupled with vulnerability to poverty, cause progressive damage to individual and family health. However, absent the legal and economic right to medical leave, workers in these contexts are generally unable to recuperate from that damage, with consequences including escalating disability and chronic illness and premature mortality [49]. It should be noted that while workers' compensation insurance can cover certain types of workplace-related injuries, the terrain of workers' compensation is rarely so expansive as to cover illness caused by overwork or labor exploitation at large. A specific injury may be covered, but workers cannot successfully claim workers' compensation benefits based on long hours and meager pay alone (for example) [50]. Therefore, absent leave eligibility, workers in these conditions may experience progressive medical deterioration, leading to eventual inability to work at all.

The FMLA protects the rights of employees to take up to 12 weeks of unpaid leave for the employee's serious health condition, to care for the employee's family member who has a serious health condition, for the birth of a child, or for the placement of a child for adoption or foster care [52]. Health and social welfare providers are key figures in assisting workers to obtain approved FMLA leave, as illness leave will require adequate documentation of the nature of the condition. Many states expand upon the rights provided by the FMLA, particularly with respect to key definitions.

The key terms that define eligibility for FMLA leave are as follows [53,54]:

The key terms that define eligibility for FMLA leave are as follows [53,54]:

As discussed, the FMLA entitles employees (as defined) to a total of 12 weeks of unpaid leave during any 12-month period for [55]:

The FMLA mandates the continuation of group health plan benefits through the duration of the employee's leave as though the employee was not on leave. However, when the period of eligible leave is over, the employer can recover premium payments made during the leave if the employee fails to return to work for reasons aside from continuation of the qualifying serious health condition or other circumstances beyond the employee's control [57].

Upon returning to work, an employee is entitled to restoration of his or her previously held position or to an equivalent position with equivalent benefits, pay, and other terms and conditions of employment. The FMLA protects benefits and seniority accrued up to the point that leave begins but does not guarantee continued accrual of benefits and seniority during the employee's absence. Employees are entitled only to the rights, benefits, or positions to which they would have been entitled had they not taken leave [58].

The FMLA excludes a large portion of the workforce by limiting coverage to public agencies and private employers with at least 50 employees. As noted, workers must also have been in their current position for at least 12 months, with a minimum of 1,250 hours of service within those 12 months. While the FMLA does cover part-time employees who meet its criteria, it does not cover newly hired employees, who frequently also do not have substantial paid time off accrued.

The FMLA allows some leeway for denial of leave or restoration for an employer's highest-paid workers if the denial is necessary to "prevent substantial and grievous economic injury" [59]. Additionally, when two spouses work for the same employer, the aggregate leave may be limited when taken for the birth or placement of a child or to care for a sick parent [60].

The FMLA typically requires 30 days' notice of intent to take leave, where practicable. When leave is foreseeable based on expected birth or placement of a child in the home or on the worker's or family member's planned medical treatment, a worker must provide the employer with notice of his or her intent to take leave not less than 30 days before the date of leave is to begin. If leave must begin in fewer than 30 days, notice must be given as soon as is practicable. When the leave is foreseeable based on planned medical treatment, the worker must, subject to the approval of the healthcare provider, make a reasonable effort to schedule the treatment "so as not to disrupt unduly" the employer's operations [61].

The FMLA permits employers to require that leave for a worker's or family member's serious health condition be supported by certification from that individual's healthcare provider, including subsequent recertification on a reasonable basis [64]. Certification of a serious health condition is sufficient if it includes [65]:

A statute of limitations sets a time frame within which a complaint must be filed in court or with a public agency. Generally, the statute of limitations for violations of FMLA rights is two years from the date of the last event constituting the alleged violation, although it may be longer for certain willful acts. State agencies have varying statutes of limitations that may be more generous than the federal statutes. Health and social welfare providers should avoid advising patients/clients as to exact deadlines for filing complaints. However, they should make patients/clients aware that statutes of limitations exist and suggest that an attorney be consulted regarding such statutes to ensure that complaints are filed within the proper time frames. Providers should also avoid withholding documentary medical support for a complaint on the basis that the provider feels too much time has passed for a patient to file a successful claim. As noted, different agencies have different deadlines, and determination of whether a complaint falls within the statute of limitations may, in some cases, be a complicated matter requiring legal expertise.

In states with large agricultural industries (e.g., California), a large portion of the labor force consists of transitory and seasonal workers. Because the FMLA requires one year of employment before a worker is eligible for leave, its protections are inaccessible to many workers due to the nature of their employment.

Workplace negotiation dynamics may be complicated for people who are dependent upon their employers for their immigration status. A worker may be facially protected under the FMLA but may still be unable to take leave due to the potential for exploitation by employers who know that their cooperation with the visa process is what allows the worker and her or his family to remain in the United States. Access to leave-taking is further complicated when the worker needs time off to care for a family member who is undocumented.

Leave-taking retaliation can come in many forms, but the following are some examples of behaviors that may constitute retaliation, particularly if the actions are catalyzed or motivated in response to leave-taking:

Providers may also play a vital role in reporting flagrant violations of family and medical leave law to appropriate governmental entities, particularly in instances in which vulnerable workers are unable or unlikely to do so. The U.S. Department of Labor's Wage and Hour Division maintains a number of resources and a toll-free number for complaints and queries and coordinates with state labor offices throughout the United States. In instances in which family and medical leave is entangled with or inextricable from other forms of civil rights violations—a common dynamic in cases involving disability or pregnancy, or based on race, age, veteran status, religion, or any other protected categories (varies by state and municipality)—providers should also consider outreach to the U.S. Equal Employment Opportunity Commission or state or municipal equivalents (e.g., local human rights or civil rights entities). Finally, providers can play a critical role in informing policymakers about the benefits and limitations of existing policy, relative to affected client/patient populations, including those who do and those who do not have sustainable leave access.