D.C. Code § 5-707

Whenever any member shall become temporarily disabled by injury received or disease contracted in the performance of duty, to such an extent as to require medical or surgical services, other than such as can be rendered by the Mayor, or to require hospital treatment, the expense of such medical or surgical services, or hospital treatment, shall be paid by the District of Columbia; but no such expense shall be paid except upon a certificate of the Mayor setting forth the necessity for such services or treatment and the nature of the injury or disease which rendered the same necessary.