What best describes Tier 4 in terms of a formulary?

Tier 4 in the context of a formulary typically refers to medications or providers that are not included in the preferred list of providers or medications that an insurance plan offers. This tier usually implies higher out-of-pocket costs for patients, as these services may not be covered under the standard terms of the insurance plan.

In contrast, the other choices do not accurately represent what Tier 4 entails in a formulary. For example, Medicare-covered providers may still fall under different tiers depending on whether they are preferred or non-preferred. Exclusive legal practitioners for insurance disputes do not pertain to formulary tiers, as they relate to legal services rather than health care coverage. Finally, premium providers with higher service fees can sometimes exist in lower tiers if they are included in a preferred network, so they would not fit the unique designation of Tier 4.