N.H. Rev. Stat. Ann. § 169-C:12-d

The court may order alcohol or drug testing at any stage of the proceeding where substance abuse is an ongoing issue in the case, where alcohol or drug use is a disputed issue of fact, or where there is reason to believe that alcohol or drug use may be substantially interfering with a parent's ability to adhere to the case plan. Unless otherwise ordered by the court, the frequency and type of such testing shall be at the discretion of the department.