INTRODUCTION:
Health ombudsman services represent a mechanism for strengthening health systems by bridging communication gaps between users and health service managers¹⁻². Evidence is present in the numerous reports received daily, enabling the evaluation and promotion of improvements in health practices, actions, and services³⁻⁴. This study evaluates the potential impact of complaints, denunciations, and compliments received by ombudsman offices to support improvements in the Brazilian Unified Health System (SUS), contributing to institutional strengthening and health policies in Brazil.

METHODS:
Secondary data analysis from recorded population contacts by SUS ombudsman offices from 1st January 2010 to July 18th, 2025, collected from the National Network of SUS Ombudsman Services panel⁵. Reports were categorized in the OuvidorSUS system. Quantitative analysis assessed recurring patterns in complaints, denunciations (negative evaluations), and compliments (positive evaluations).

RESULTS:
During the study period, 5771724 recorded contacts were registered by the National Network of SUS Ombudsman Services in municipalities, states and the Ministry of Health. Complaints (2030797- 35.19%) addressed issues such as barriers to access or book appointments, examinations, and health facilities, dissatisfaction with health professionals, and lack of medications. Denunciations represented 563739 reports (9.77%), addressing topics such as commercial establishments under health surveillance, health professionals, refusal of care, among others. Compliments (422646- 7.32%) addressed satisfaction with health professionals, praising healthcare workers such as physicians, nurses, and other professionals), quality of food services, and physical facilities.

CONCLUSIONS:
Health ombudsman services function as powerful evidence generators for health system strengthening when integrated into quality improvement structures (planning)⁶. Systematic analysis of complaints and denunciations identifies critical system vulnerabilities, which can be described by location and service, enabling targeted interventions. Meanwhile, compliments represent positive evaluations that can be replicated as good practices in health. Scaling these approaches through ombudsman offices could transform health governance globally, utilising population evaluation data regarding health systems⁷.