Dyfrig has led the pharmacoeconomic activities of the All Wales Therapeutics and Toxicology Centre, contributing to over 200 substantive Health Technology Assessment reports informing medicines policy in Wales. He is a current member of the All Wales Medicines Strategy Group, and past member of the NICE technology appraisal committee. He chairs the pharmacogenomics test evaluation working group for the Genomics Programme in NHS England and NHS Improvement, and is also pharmacogenetics champion for the Royal Pharmaceutical Society. Dyfrig is also expert advisor to the Committee for Orphan Medicinal Products of the European Medicines Agency.

In 2016, Dyfrig was awarded Health and Care Research Wales Senior Research Leader (equivalent to NIHR Senior Investigator). He was inaugural president (and honorary member) of the International Society for Medication Adherence and is an elected fellow of: The Learned Society of Wales, The British Pharmacological Society, and the Faculty of the Royal Pharmaceutical Society. He is also an editorial board member of the journals PharmacoEconomics and Clinical Pharmacology & Therapeutics, and Executive Editorial Board member of the British Journal of Clinical Pharmacology and BMC Orphanet Journal of Rare Diseases.