Dr Rajaratnam obtained a BSc in pathology with honours in 2001 and graduated from the University of Birmingham Medical School. She then completed her specialist training in dermatology in the West Midlands, United Kingdom, and underwent further fellowship training in lasers and cosmetic dermatology at the University of Ottawa, Canada. Apart from her clinical commitments, Dr Rajaratnam has presented papers at local, regional and international meetings.

Before moving back to Singapore, Dr Rajaratnam was a consultant at the University Hospital Birmingham NHS. She has since been a part of Changi General Hospital (CGH) as a senior consultant and her practice includes all aspects of dermatology with interests in medical dermatology and eczema.