Relational stigma as a social determinant of health: “I'm not what you _____see me as”

•Stigma done by others, and internalised by participants, meant that PWUD experience harms to mental and physical health.•Stigma should be considered a social determinant of health because social relations structure an ‘invisible reality’.•Stigma, impacts a person's physical and mental health and is a pernicious problem that exacerbates health inequalities.•Social relations acting in synergy with psycho-social and material determinants of health is an under-researched area.