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HEDIS Adherence Without the Headaches: How PDC Gaps Happen and How to Close Them

By Medication Call Reminder · 2026-09-23

PDC gaps rarely come from one large failure. They often begin with a missed reminder, a prescription change, a discharge transition, or incomplete visibility across pharmacies. Here is how quality teams can identify those moments, support patients consistently, and turn adherence activity into actionable reporting data.

Excerpt: PDC gaps rarely come from one large failure. They often begin with a missed reminder, a prescription change, a discharge transition, or incomplete visibility across pharmacies. Here is how quality teams can identify those moments, support patients consistently, and turn adherence activity into actionable reporting data.

Quality teams are expected to improve medication adherence while working with incomplete information, competing priorities, and limited staff time. A patient may appear stable in the record, yet a prescription change, hospital discharge, refill delay, or pharmacy transfer can create a gap in coverage.

By the time the gap appears in claims data, the most useful intervention window may have passed.

A practical HEDIS medication adherence tool should help your team do more than display a percentage. It should help you understand where adherence support breaks down, provide a consistent way to follow up, and preserve an objective activity history for review.

That is the operational purpose of a medication adherence program for clinics: make adherence support visible, repeatable, and easier to act on.

HEDIS Measures Put Daily Adherence Into a Quality Framework

HEDIS is a widely used set of health care performance measures developed and maintained by the National Committee for Quality Assurance (NCQA).

Medication adherence measures evaluate whether eligible patients have medication coverage across a defined treatment period. In Medicare Part D Star Ratings, CMS uses PDC-based measures for:

• Diabetes medications
• Hypertension medications, including renin-angiotensin system antagonists
• Statins for cholesterol management

The exact measure specifications, eligibility rules, exclusions, medication lists, and reporting requirements can vary by program and measurement year. Quality teams should use the current applicable NCQA, CMS, payer, and contract specifications when calculating or submitting performance results.

How PDC Is Calculated

The basic PDC formula is:

PDC = covered days ÷ days in the treatment period

Prescription claims establish the covered days. The treatment period is defined by the applicable measure specification. A patient’s PDC is then expressed as a percentage.

For example, if a patient has 270 covered days in a 300-day treatment period:

270 ÷ 300 = 90% PDC

Many CMS medication adherence measures use an adherence threshold of 80%, but the threshold and calculation rules should always be confirmed against the current measure specifications. CMS explains the calculation methodology, including overlap handling and facility-stay adjustments, in its 2026 Part C & D Star Ratings Technical Notes.

PDC is not simply a count of prescription fills. It considers whether the patient has coverage across calendar days. Overlapping fills, changes within a therapeutic category, inpatient stays, skilled nursing facility stays, and other measure-specific rules may affect the calculation.

That distinction matters. A patient can have multiple fills and still experience an avoidable coverage gap.

PDC Gaps Begin at Specific Points in the Patient Journey

A low PDC is an outcome. To close the gap, your team needs visibility into the moment when coverage or routine begins to break down.

1. After hospital discharge

Discharge creates a high-risk workflow point for medication routines. The patient may return home with:

• A new prescription
• A discontinued medication
• A changed dose
• A different administration schedule
• Instructions from several care settings
• A short supply that requires prompt refill coordination

CMS and NCQA separately address medication reconciliation and transitions of care. Those processes help confirm what the patient should take. They do not, by themselves, confirm that the patient has established a workable routine once home.

A reminder program can support the operational follow-up after reconciliation. It can help the care team see whether the patient responds to reminders and whether additional outreach may be needed.

Medication instructions and changes must come from the prescribing provider or pharmacist. Patients should not start, stop, combine, or change medications based on an automated reminder or adherence report.

2. After a prescription change

A prescription change can interrupt an established routine. The patient may continue following an old schedule, wait for clarification, or become uncertain about which medication belongs in the daily routine.

A reminder system should not decide which prescription is clinically appropriate. It should support the schedule entered by the authorized care team and preserve a record of reminder activity.

When the medication list changes, the provider or pharmacist should verify the current instructions before the reminder schedule is updated. The FDA’s medication safety guidance recommends discussing medication changes with a doctor or pharmacist and keeping an up-to-date medication list.

3. When multiple pharmacies are involved

Patients may use one pharmacy for maintenance medications, another for specialty prescriptions, and a mail-order service for longer supplies. A pharmacy transfer, insurance change, or stock issue can make it difficult for the patient and care team to see the complete picture.

Claims data may eventually show the result. The immediate workflow problem is coordination.

A clinic-based adherence program can provide one support layer across the patient’s routine, regardless of where a prescription is filled. The system does not replace pharmacy records or claims data. It adds patient-level activity that can help your team determine whether the patient received a reminder, responded, missed a scheduled confirmation, or may need follow-up.

Objective Activity Turns Assumptions Into Action

Without patient-level activity, a care team may have to rely on assumptions:

• The patient probably knows the schedule.
• The prescription was probably picked up.
• The family member probably noticed the missed dose.
• The patient probably continued after discharge.
• The refill probably occurred on time.

Those assumptions are difficult to operationalize and difficult to report.

A stronger workflow separates three types of information:

Reminder confirmations are useful activity data, but they are not proof that a medication was ingested. A “taken” response records what the patient reported. It should be interpreted as adherence-support activity, not as a clinical finding or substitute for claims-based measurement.

This distinction strengthens reporting integrity. Your team can use claims for formal PDC calculations while using reminder and response history to understand where support was delivered and where follow-up may still be appropriate.

What a Provider-Ready Adherence Solution Should Include

The right solution should fit into existing workflows instead of creating another disconnected queue.

Voice reminders that patients can answer by phone

Voice calls provide a direct, familiar channel for patients who do not use apps consistently or who prefer telephone communication. A reminder can be configured for the schedule established by the care team.

SMS notifications for simple confirmations

SMS gives patients a brief way to receive and respond to reminders. It can be useful for patients who prefer text messages or need a written prompt.

Real-time caregiver or care team alerts

When a patient misses a scheduled confirmation, an alert can notify the designated caregiver or authorized care team member. This helps move outreach from periodic review to a more timely workflow.

Family coordination is a separate use case. Families may use reminders and alerts to support a loved one at home. Providers need patient-panel visibility, role-based access, reporting, and documented workflows. Medication Call Reminder offers distinct support for those family and provider needs rather than treating them as the same experience.

Adherence history and patient management tools

A provider portal should allow teams to review activity by patient and across a panel. Medication Call Reminder’s provider portal demo includes sample views for confirmed activity, missed activity, recent medication events, and refill-related information.

The goal is not to replace clinical judgment. It is to give staff a clearer starting point for appropriate follow-up.

Exportable reports for quality workflows

Quality teams need data that can be reviewed, shared, and incorporated into existing processes. Medication Call Reminder provides adherence tracking, reporting, and exportable compliance information designed to support PDC calculation workflows.

The platform does not independently establish an official HEDIS result. Your organization remains responsible for applying the current measure specifications, validating source data, and determining how the information is used for reporting.

Medication Call Reminder Supports the Gap-Closure Workflow

Medication Call Reminder is designed as a medication adherence solution for providers that combines:

• Personalized voice calls
• SMS reminders
• Patient confirmations
• Missed-dose alerts
• Caregiver and care team notifications
• Patient-level adherence history
• Provider management tools
• Exportable compliance reports
• Panel-level visibility for participating staff

The workflow is straightforward:

1. Set up the patient panel. Add the patient, authorized medication schedule, contact preferences, and alert recipients.
2. Send scheduled reminders. Patients receive a voice call or SMS prompt.
3. Capture the response. The system records the patient’s confirmation or missed response.
4. Route exceptions. Designated recipients receive an alert when follow-up may be needed.
5. Review the history. Staff see activity over time instead of relying on a single point-in-time assumption.
6. Export data for review. Teams can use adherence activity alongside claims and other approved data sources.

The platform is built for clinics, practices, agencies, and value-based care teams that need a scalable support layer. It is designed with privacy-conscious infrastructure, audit logging, PHI safeguards, HIPAA compliance objectives, and BAA readiness in mind. Organizations should review their own compliance, contracting, security, and integration requirements before deployment.

See the Medication Call Reminder provider services or review provider pricing and reporting options.

Close PDC Gaps With Better Visibility

PDC gaps are often created by ordinary workflow disruptions: a discharge, a prescription change, a missed refill, or a fragmented pharmacy experience.

The response does not need to be complicated. Your team needs:

• A consistent patient contact method
• Clear exception alerts
• Objective activity history
• A defined follow-up process
• Reporting that can be reviewed alongside claims data

Medication Call Reminder provides adherence support infrastructure. It does not prescribe, change, or stop medications. Those decisions remain with the patient’s prescribing provider and pharmacist.

Request a provider portal demonstration to review the workflow, reporting capabilities, and BAA-readiness requirements for your organization.

Trusted Resources

• NCQA HEDIS Measures and Technical Resources
• CMS 2026 Part C & D Star Ratings Technical Notes
• FDA: Stop, Learn, Go, Tips for Talking to Your Pharmacist
• FDA: Buying and Using Medicine Safely