Preserving Rules Ordered for The Entities Covered Through 340B Act of 2021 or the PROTECT 340B Act of 2021 This bill prohibits pharmacy benefit managers (PBMs) and health insurance plans from discriminating against health providers participating in the 340B drug pricing program, including pharmacies contracted with such providers to dispense 340B drugs. The 340B program allows certain providers to receive covered outpatient drugs at reduced prices from manufacturers. Specifically, PBMs and insurance plans may not reimburse 340B participants at a lower rate than other entities not participating in the program; impose differing terms (such as fees, charge-backs, or audits) on 340B participants; interfere with an individual's choice to receive drugs from a 340B participant; require 340B participants to identify which drugs fall within the program; or refuse to contract with a 340B participant on the basis that they utilize the program. Violations of this bill are subject to a civil penalty of not more than $5,000 per violation per day. These prohibitions also apply to prescription drug (Part D) sponsors under Medicare. The bill also provides for a process to prevent duplicate 340B drug discounts to states under Medicaid.