Creating Transparency to Have Drug Rebates Unlocked (C-THRU) Act of 2019 This bill establishes a series of requirements relating to drug rebates and discounts under Medicare and Medicare Advantage (MA). Specifically, for each pharmacy benefits manager (PBM) that contracts with a prescription drug plan (PDP) under Medicare or MA, or with a qualified health benefits plan offered through a health insurance exchange, HHS must publish on its website (1) the amount and type of rebates and discounts negotiated by the PBM and the extent to which these rebates and discounts are passed on to the plan sponsor, and (2) the difference between the amount paid by the plan sponsor to the PBM and the amount paid by the PBM to pharmacies. As a condition of participation as a contractor under Medicare or MA, a PBM must pass on to a PDP sponsor a minimum percentage, as established by HHS, of the amount of rebates and discounts negotiated by the PBM that are attributable to patient utilization under the plan. The bill also modifies requirements regarding Medicare enrollees' access to negotiated drug prices. Current law requires a PDP sponsor to provide enrollees in Medicare or MA with access to negotiated drug prices that account for rebates and discounts. The bill requires that, with respect to a covered drug, a negotiated price (or, if necessary, an approximate negotiated price) be provided at the point of sale.