Evidence base: key studies
| Study | N | Setting | Reduction |
|---|---|---|---|
| JMIR 2019 meta-analysis (primary) | 14 RCTs | Healthcare (mixed) | 28-38% SMS |
| JAMA 2018 | ~200K appts | Primary care US | 22% SMS, 14% email |
| BMJ 2012 | ~48K appts | UK outpatient | 38% SMS two-way |
| JABFM 2015 | ~12K appts | Family medicine US | 28% automated call |
| JMIR 2021 (telehealth) | ~85K appts | Behavioral health | 25% telehealth option |
Optimal timing
48 hours before
Full reminder with all details
22% reduction alone
2 hours before
Brief confirmation prompt
+12-16% additional
No reply by T-4hr
Staff callback + waitlist notify
Mitigates remaining gap
SMS vs email vs phone
SMS (two-way confirmation)
28-38%Highest effectiveness, fastest
SMS (one-way)
20-25%Good baseline
Email
15-20%Additive to SMS, not replacement
Phone call
35-45%Most effective per contact, not scalable
Patient portal message
10-15%Additive for established patients
TCPA compliance for healthcare SMS
The Telephone Consumer Protection Act (TCPA) requires TCPA-compliant written consent before sending automated SMS messages to US mobile numbers. For healthcare appointment reminders:
- *Obtain express written consent at patient intake (paper or digital form)
- *HIPAA-covered entities: appointment reminders are "treatment, payment, operations" communications - consent is implicit if the patient provided their number
- *Always provide an opt-out mechanism (reply STOP)
- *Restaurant and salon reminders require explicit opt-in as they are commercial messages
- *Most reminder platforms (Weave, SolutionReach, Fresha) handle TCPA compliance automatically
FAQ
Do SMS reminders work for reducing no-shows?+
Yes. A 2019 JMIR meta-analysis of 14 randomised controlled trials found SMS reminders reduce healthcare no-shows by 28-38%. This is the strongest evidence-base of any single intervention. Two-way confirmation (requiring the patient to reply) adds approximately 15% effectiveness on top of one-way reminders.
How many reminders should I send?+
The evidence supports two reminders: one 48 hours before the appointment and one 2 hours before. Three or more reminders do not significantly improve outcomes over two and increase opt-out rates. The 48-hour reminder should include the full appointment details. The 2-hour reminder should be brief and action-focused.
Is SMS or email better for appointment reminders?+
SMS significantly outperforms email for no-show reduction. SMS open rates are 98% versus 20-30% for email. The JMIR 2019 data shows SMS achieves 28-38% reduction versus 15-20% for email. However, email adds an additional 8-12% reduction when combined with SMS, making both together the optimal strategy.