29 CFR § 825.119 - Leave for treatment of substance abuse.
(a) Substance abuse may be a serious health condition if the conditions of §§ 825.113 through 825.115 are met. However, FMLA leave may only be taken for treatment for substance abuse by a health care provider or by a provider of health care services on referral by a health care provider. On the other hand, absence because of the employee's use of the substance, rather than for treatment, does not qualify for FMLA leave.
(b) Treatment for substance abuse does not prevent an employer from taking employment action against an employee. The employer may not take action against the employee because the employee has exercised his or her right to take FMLA leave for treatment. However, if the employer has an established policy, applied in a non-discriminatory manner that has been communicated to all employees, that provides under certain circumstances an employee may be terminated for substance abuse, pursuant to that policy the employee may be terminated whether or not the employee is presently taking FMLA leave. An employee may also take FMLA leave to care for a covered family member who is receiving treatment for substance abuse. The employer may not take action against an employee who is providing care for a covered family member receiving treatment for substance abuse.