(a) No insurer, health care center, hospital service corporation, medical service corporation or other entity delivering, issuing for delivery, renewing, continuing or amending any group health insurance policy providing coverage of the type specified in subdivisions (1), (2), (4), (6), (10), (11) and (12) of section 38a-469 in this state shall deliver or issue for delivery in this state any such policy unless such policy contains a definition of “medically necessary” or “medical necessity” as follows: “Medically necessary” or “medical necessity” means health care services that a physician, exercising prudent clinical judgment, would provide to a patient for the purpose of preventing, evaluating, diagnosing or treating an illness, injury, disease or its symptoms, and that are: (1) In accordance with generally accepted standards of medical practice; (2) clinically appropriate, in terms of type, frequency, extent, site and duration and considered effective for the patient’s illness, injury or disease; and (3) not primarily for the convenience of the patient, physician or other health care provider and not more costly than an alternative service or sequence of services at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of that patient’s illness, injury or disease. For the purposes of this subsection, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community or otherwise consistent with the standards set forth in policy issues involving clinical judgment.

(b) The provisions of subsection (a) of this section shall not apply to any insurer, health care center, hospital service corporation, medical service corporation or other entity that has entered into any national settlement agreement until the expiration of any such agreement.

See https://www.cga.ct.gov/current/pub/chap_700c.htm