I recently received notice that my employer-sponsored Aetna healthcare plan will drop Dexcom CGMs from its formulary and adopt Abbott FreeStyle Libre instead. Some might be unhappy, but I welcome the change. Based on my experience with both products, I consider Libre a superior CGM.
Libre provides new glucose updates every minute, compared with every five minutes with Dexcom G7, or 1,440 updates per day vs. 288. Abbott also earned credit for bringing meaningful price competition to the U.S. CGM market. Libre originally offered 14 days of wear, four days longer than Dexcom's sensor at the time (which translated into Libre being about 30% cheaper given the cost of each brand of sensors), reducing the effective cost per day of usage for patients. Dexcom has since responded with the 15-day G7 Plus, although Abbott matched that with the Libre 3 Plus. But Abbott was the company that initially introduced the longer wear-time advantage which reduced patient out-of-pocket costs. That is what competition is supposed to do.
My good friend Riva Greenberg made the same switch from Dexcom to Libre and has been happy with her decision. She wrote about her firsthand experience with Dexcom G7 here: https://diabetesstories.com/2023/07/21/im-sorry-to-say-im-not-loving-dexcoms-g7/.
But my formulary isn't becoming more competitive. Its simply switching the preferred brand from Dexcom to Freestyle Libre. That's not restoring patient choice. In an ideal world, both Dexcom and Libre would be covered, with differences in negotiated costs reflected in patient co-pays or other cost-sharing.
There's another wrinkle in the formulary change that caught my attention. The notice says FreeStyle Libre now requires preauthorization and is limited to 2 sensors every 25 days. The quantity limit every 25 days is no different from what I now have with Dexcom. But my previous Dexcom coverage didn't require prior authorization. That strikes me as particularly bad because PBMs and insurers have been under increasing pressure to reduce prior authorizations, and yet here I am getting a new prior-authorization requirement in addition to my switching preferred CGM brands which presumably saves it money.
So while Aetna and Caremark are giving me a CGM I consider to be superior, they appear to be taking something away at the same time by adding a new prior-authorization requirement that did not apply to Dexcom. Giving with one hand and taking away with the other while enriching themselves is a pretty good description of how I have come to view PBMs and health insurers.
There are some important differences between the two CGM companies. Dexcom currently has more established U.S. partnerships with automated insulin delivery (AID) systems, including non-exclusive partnerships with Insulet and Tandem. FreeStyle Libre does not currently have a functional AID system in the U.S. with either of those companies. The differences matter to patients, particularly people using AID systems. But none of that matters much to a PBM when there is money to be made from deciding which manufacturer gets preferred formulary status.
For a long time, CVS Caremark (which owns the insurance company Aetna) maintained a formulary exclusion for any CGMs which "Are not Dexcom Brand." How Dexcom was persuaded to pay PBMs huge rebates conditioned on excluding competing CGM brands was kind of foolish in my view. Even without a formulary exclusion, Caremark was never going to cover a competing CGM, so the rebates Dexcom paid to CVS Caremark to keep Libre "off formulary" was money being pissed away for nothing.
There is, however, a glaring exception to Caremark's Freestyle Libre exclusion on my plan. Aetna also covers Senseonics' Eversense 365 CGM, but there is a simple explanation: Eversense is covered under the medical benefit rather than the pharmacy benefit because a physician must insert the Eversense sensor in a patient's arm rather than having the patient insert it themselves.
That meant Caremark could (on paper) honor its commitment to keep competing CGMs off its pharmacy formulary while Aetna also covers a competing CGM through the medical benefit. From the patient's perspective, a competing product was technically available, but only by going through a different part of the insurance plan. It is exactly the kind of disjointed, fragmented coverage structure and deceptive and opaque business practices that makes me skeptical of PBMs and the way they control access to prescription products.
The same dynamic existed with UnitedHealthcare plans, where Optum Rx collected rebates while competing CGMs were excluded from its preferred prescription formularies. Eversense covered as a medical benefit on United Healthcare plans is a work-around for the insurance companies, but the companies paying the rebates are being promised something they are not actually receiving.
This is where the Federal Trade Commission's litigation against the largest PBMs becomes relevant. In September 2024, the FTC sued Express Scripts, CVS Caremark and Optum Rx and their respective GPOs in the same underlying proceeding over alleged anticompetitive practices involving insulin pricing, rebates and formulary exclusions. The FTC subsequently negotiated separate settlement agreements with each PBM.
On July 14, 2026, CVS Caremark agreed to settle with the FTC without admitting wrongdoing and agreed to substantial changes in how its PBM business operates.
The Express Scripts and Caremark settlement agreements are largely parallel. Much of the relief had already been outlined in the FTC's contemplated relief in the underlying litigation. Adam Fein at Drug Channels summarized the practical implications of the settlement agreements: https://www.drugchannels.net/2026/02/the-ftc-blows-up-express-scripts-pbm.html
Among the changes the FTC settlement agreements will impose include:
- Standard formularies can no longer favor high-WAC drugs over lower-WAC alternatives [WAC is the acronym for "Wholesale Acquisition Cost" which is another term for a pharmaceutical's list price]
- Patient out-of-pocket costs are to be be based on the PBM's discounted "net" price rather than the artificially-inflated list price under the applicable settlement arrangements
- Plans and beneficiaries have access to direct-to-consumer pricing through TrumpRx
- Point-of-sale rebates must be passed through to patients
- Manufacturer fees paid to PBMs must be de-linked from pharmaceutical list prices
- Employer healthcare plan sponsors receive substantially more transparency
- Retail pharmacies can receive cost-plus reimbursement
The FTC's Express Scripts settlement announcement is here:
The full Caremark settlement document is here:
So why does this matter to me?
I am getting the CGM I would prefer to use because I think it's superior. But I have no idea whether that's because Abbott offered Aetna or CVS Caremark a better "net" price, or because of some other contractual arrangement. Patients generally are not told what actually drives these decisions.
That is the part I find interesting: The FTC is trying to change the financial incentives that have shaped PBM formularies for years, yet my own experience suggests that the fundamental structure remains unchanged so far. One manufacturer has preferred status and the competing manufacturer is effectively excluded. The only thing that has changed is which manufacturer won.
And now there is another question: insurance companies pledged in June 2025 (see https://kffhealthnews.org/insurance/prior-authorization-insurance-denials-reform-pledge-year-later/ for more) to improve a controversial practice known as "prior authorizations," which requires patients or someone on their medical team to seek prior approval from insurers before proceeding with treatments, so why is my Aetna plan apparently now adding a brand new prior auth requirement for a CGM at the same time it also changes which brand of CGM is preferred? That would seem to be a direct contradiction to the prior commitment Aetna made to end prior authorizations, which burdens patients and doctors with unnecessary delays in care.
In an ideal world, both Dexcom and Libre would both be covered (and that's how things used to be done in the past). Patients could choose the product that works best for them, while negotiated differences in cost could be reflected through patient cost-sharing rather than "formulary exclusion". Now, the settlement agreements specify "as soon as commercially feasible, but no later than the implementation date of Month DD, YYYY" so I realize these could still be modified. But knowing how Caremark operations, I won't hold my breath waiting.
In this case, I happen to be OK with the outcome because the preferred manufacturer is the one I would likely choose anyway. But that does not mean my formulary has become more competitive or transparent. It has simply switched the preferred brand from Dexcom to Libre.
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