A number of applications based on personal health records (PHRs) are emerging in the field of health care and wellness. PHRs empower patients by giving them control over their health data. Health data for PHRs can be supplied by patients, wellness providers and health care providers. Health care providers may use the PHRs to provide medical care. Unfortunately, the quality of the health data in PHRs cannot be guaranteed in all cases. For example, consider cases where non-professionals such as patients and wellness providers supply data. To address this problem, we present in this paper a system that provides health care professionals with an indication of the quality of health data in a PHR. This indication is based on the reputation of the supplier and on metadata provided by measurement devices. The proposed reputation system mimics the way in which trust in health data and their suppliers is built in the real world. The system introduces minimal overhead for health care providers and patients.