Janaka graduated with a distinction in medicine from the University of London and was awarded UK Medical Research Council Clinical Research Training Fellowship and PhD (supervisor Professor Giancarlo Viberti) by the University of London for research on the pathophysiology and treatment of cardiovascular disease and renal disease in diabetes.

He is an active clinician working with more than 20 years of experience and specialist expertise managing patients with kidney and cardio-vascular complications related to diabetes at Guy’s and St Thomas Hospital. He has established community based clinics in London working with primary care colleagues focussed on early identification and treatment to reduce cardiovascular and kidney complications. Janaka is a clinical scientist with a research focus on the pathophysiology and treatment of cardio-renal complications in people with diabetes. He has a programme of experimental research focussed on new strategies for the treatment of diabetic renal, retinal and cardiovascular disease. His group recently reported the first evidence that people of African-Caribbean heritage with type 1 diabetes are at increased risk of kidney and eye complications of diabetes as compared to people from other heritages. Recent work has elucidated the role of anti-ageing cardio-renal protective hormone Klotho on microvascular diabetes complications, the role of arterial ageing on kidney complications and the efficacy and safety of using advanced hybrid close loop insulin delivery systems (‘artificial pancreas’) in people with diabetes and kidney failure on haemodialysis. He has led an award winning programme of work on risk stratification and clinical prioritisation [Health Service Journal digital award (2023), Quality in Care diabetes award (2024), Royal College of Physician excellence in patient care awards (top three 2025)] that enables early identification and clinical prioritisation of people with modifiable risk that is now embedded in routine care.

He speaks frequently at national and international meetings and has published more than 100 articles on cardio-renal disease. He has led on UK Kidney Association (UKKA) and Association of British Clinical Diabetologists (ABCD) diabetic kidney disease guidelines and is the co-chair of this working group.

Janaka lectures, supervise research projects and examines in a number of undergraduate and post graduate degree courses (PhD, MD and MSc) programmes. He the associate editor for European Federation of Internal Medicine (EFIM) education academy leading on cardio-renal-metabolic education, an associate editor for Diabetologia the journal of the European Association for the study of diabetes (EASD) and a member of the EASD teaching and education committee.