Rajna is Associate Executive Director of the NNEdPro Global Institute for Food, Nutrition and Health. Rajna has been a lead investigator in the NNEdPro team over more than a decade. Rajna has been active in teaching medical students and is associate editor of the Oxford Handbook of Clinical and Healthcare Research.

She is an NIHR Clinical Lecturer in Diabetes & Endocrinology at the University of Oxford where she is providing clinical service and doing research revolving around type 2 diabetes and cardiometabolic disorders. Rajna is the principal investigator of a large-scale pharmacoepidemiologic study focusing on using real world data from inpatients to improve the detection and management of glucocorticoid-induced diabetes. This study is funded by the Association of British Clinical Diabetologists (ABCD).

Prior to coming to Oxford, Rajna was an NIHR Academic Clinical Fellow in Diabetes & Endocrinology at the University of Cambridge where she was a co-investigator on several trials conducted as a partnership between academia and industry with a more prominent focus on novel treatments such as dual agonists (cotadutide- GLP1/glucagon agonist). She has been awarded a pump priming grant from the Diabetes Research and Wellness Foundation as a principal investigator of a proof-of-concept study focusing on the effects of serotonin receptor agonism on glucose homeostasis. Rajna was the national winner of the Royal College of Physicians Turner-Warwick lecturer competition in 2021.

She completed an MPhil in Public Health and a PhD in Epidemiology (MRC Epidemiology Unit) at the University of Cambridge as a Gates Cambridge scholar. Her work focused on physical activity and cardiometabolic risk in the context of large-scale cohort studies.