He now works in private practice and has a post of consultant at the Tavistock & Portman NHS Foundation Trust where he has worked for the past 20 years. He specialises in the treatment of a range of clinical problems, including depression, anxiety and more complex personality problems. He has a particular interest in understanding and helping people with a variety of difficulties, including problems with imposing their authority, or being overly controlling. He specialises in treating people who suffer with psychosexual difficulties, including sex addiction, and managing and expressing their feelings of anger. He is based at the Tavistock Centre and in the West End.

Dr Blumenthal trained as a clinical psychologist and received his doctorate in 1997. He is an Associate Fellow of the British Psychological Society. He then undertook a four year training to become a psychotherapist at the Tavistock Clinic, which he completed in 2005. He followed this with a further six year training in psychoanalysis, an intensive form of psychotherapy, at the Institute of Psychoanalysis and gained his membership of the British Psychoanalytical Society in 2012. He is a fellow of the Institute of Psychoanalysis. He currently works at the Portman Clinic, part of the Tavistock & Portman NHS Foundation Trust. In his NHS post, he is head of research and is involved in training for the Clinic. He works to the highest ethical standards of his profession and he is regulated by both the Health and Care Professions Council (HCPC) and the British Psychoanalytic Council (BPC).

In addition to his clinical, research and teaching work, Dr Blumenthal is an experienced supervisor and consultant. He offers individuals and teams supervision and consultation to understand the people they are working with. He has a particular interest in understanding the connection between the mind and behaviour, and the risk of acting out in ways which are harmful to self and others. He has recently published a book on this subject called Assessing Risk: A Relational Approach. As well as his trainings in psychology, psychotherapy and psychoanalysis, he is also trained in Mentalisation-Based Therapy (MBT). He regularly undertakes various teaching engagements, including conferences and has done so locally and internationally.