Wash. Rev. Code § 41.05.188
(1) Each health benefit plan offered to public employees and their covered dependents under this chapter that is not subject to chapter 48.43 RCW and that is issued or renewed after December 31, 2015, must offer benefits or coverage for medically necessary elemental formula, regardless of delivery method, when a licensed physician or other health care provider with prescriptive authority:
[ 2014 c 115 s 1.]