Medication Nonadherence: Why Patients Miss Doses, Health Systems Miss the Signs

Medication nonadherence costs the US health care system an estimated $100 to $300 billion annually, of which roughly 1 in 5 new prescriptions is never filled. Among those filled, approximately half are taken incorrectly in terms of timing, dosage, frequency, or duration.¹

New research presented today at the 2026 Pharmacy Quality Alliance (PQA) Annual Meeting in Baltimore, Maryland, offers dose-level evidence that reframes how medication adherence should be measured, who is most at risk, and when that risk first appears.²

Synchronyx, the digital health company behind the Tappt Health platform, presented findings that draw on a cross-therapy, multi-institution dataset, extending the company's PQA Gold Medal-recognized work in oral oncology adherence to a broader population spanning multiple disease areas and care settings.

"When patients have a real-time, low-friction channel to tell you what is happening with their medication, the data they generate does not look like what the field has assumed," Tamar Sapir, PhD, CEO of Synchronyx, said in a news release. "Forgetfulness is real, and it is present. But alongside it, we are seeing patients actively managing side effects they have not told anyone about, navigating supply failures that no refill system would catch, and making considered decisions about a therapy whose necessity they are still weighing.”

The Problem with How Adherence Is Measured Today

The 2 dominant metrics used to assess medication adherence, proportion of days covered (PDC) and medication possession ratio (MPR), are both derived from pharmacy refill records. A prescription refilled is not a dose taken. At the same time, a dose not taken is not necessarily disengagement; it may be a provider-directed clinical pause, a supply chain failure, an unreported side effect, or an unmet informational need that the patient has no channel to communicate, according to Synchronyx.

In other words, these metrics detect a supply gap, not a behavior gap. However, they detect it weeks or months after the moment when a timely intervention could have made a difference.

The Highest-Risk Window Is Earlier Than Most Programs Assume

The analysis confirms that patients are most likely to disengage in the earliest weeks of treatment, a period when new medication routines are fragile, side effects are novel, and concerns about necessity and safety are most active.

This is also the period that refill-based monitoring structurally cannot see. By definition, a refill-based alert cannot fire before the first refill cycle has elapsed, meaning the gap between when risk emerges and when it becomes measurable by conventional tools is precisely the window when early intervention would be most effective.

For health plans relying on PDC data to identify at-risk members and trigger outreach, this timing mismatch is not a minor inefficiency; it is a systematic failure to act when action is most likely to matter.

Not All Nonadherence Is the Same

When patients are given a low-friction, real-time channel to report a missed dose, the reasons they provide span the full behavioral spectrum: adverse effects and medication concerns (intentional, belief-driven), forgetfulness and disrupted routine (unintentional, habit-based), and supply or access failures (structural).

This distinction is clinically critical. Behavioral strategies effective for habit-based forgetting, such as reminders, implementation intentions, and cue-routine-reward structures, are ineffective and potentially counterproductive for patients whose nonadherence is rooted in active ambivalence about their therapy. Designing a one-size-fits-all adherence intervention is not just inefficient; it may actively underserve the patients at highest risk.

Some "Nonadherence" Is Actually Clinically Directed

A finding with significant implications for quality measurement: a meaningful share of what conventional metrics count as nonadherence is clinically intentional. Provider-directed treatment pauses are a routine feature of oncology and chronic disease management. PDC and MPR-based calculations absorb these pauses as adherence failures, inflating the apparent problem and mischaracterizing the patient-provider relationship.

This matters not only for the accuracy of individual patient records but also for the validity of any outcomes research or quality analysis built on adherence data. If the denominator is inflated with misclassified events, every downstream analysis is compromised.

Overall, with nonadherence already linked to 125,000 preventable deaths and up to $300 billion in avoidable costs each year, the shift from supply-side proxies to real-time, patient-reported data is not an incremental improvement; it is the infrastructure change the field has needed all along.

References

1. Neiman AB, Ruppar T, Ho M, et al. CDC Grand Rounds: improving medication adherence for chronic disease management—innovations and opportunities. MMWR Morb Mortal Wkly Rep. November 17, 2017. Accessed May 13, 2026. https://www.cdc.gov/mmwr/volumes/66/wr/mm6645a2.htm

2. At PQA 2026, Synchronyx makes the case for real-time medication intelligence: why patients miss doses, and when risk actually surfaces. News release. Synchronyx. May 13, 2026. Accessed May 13, 2026. https://www.synchronyx.com/blog/pqa-2026-reasons-for-nonadherence