Ratanui Medical has been a group practice in Henderson for over 50 years with a long history of commitment to provide medical care to the community. The practice moved from Ratanui Street to Lincoln Road in 1989 to be in a purpose built building. The two principal doctors are Dr Chris Wong and Dr Joanna Lang working with seven assistant GPs, a GP Registrar and a team of nurses and administration staff.


Dr John Caldwell
John is committed to general practice, having completed his Fellowship in 2014. He encourages an activity based lifestyle for healthy living and tries to set a good example by cycling and playing tennis in his spare time.



Dr Chris Wong
Chris is an Honorary clinical teacher with the University of Auckland and teaches medical students and GP Registrars.  He has an interest in minor surgery and performs vasectomies.  Chris is a keen tennis player.



Dr Joanna Lang
Joanna is originally trained in Poland and has an interest in women and child health. She is fluent in Polish and likes the performance arts when she is not busy in the garden.



Dr Cassie Granek
Cassie is originally from Australia and has now made West Auckland her home. She has two young daughters and enjoys teaching them to appreciate our amazing environment. She works part time and is interested in travel medicine, Maori and Pacific Health.

Dr Cassie Granek is on sabbatical leave in The Netherlands during 2019. She plans to return in early 2020.



Dr Saville Marquis
Saville is an overseas trained doctor. After becoming registered in NZ, he has worked in Whangarei Hospital and clinics in West Auckland including Ratanui Medical Centre as a GP Registrar. He has now returned to Ratanui to work full time. Saville loves sports and in particular cricket.



Dr Tilda Samuelson
Tilda trained in Scotland and London and was working in London as a GP prior to moving to New Zealand with her young family. She loves all aspects of GP care.



Dr Abigail Smith (Abby)
Abby is from Northland and trained at Auckland Medical School. She works part-time as she has three preschool aged children. She has a particular interest in Women's Health and Paediatrics. Abby shares the practice with Dr Tilda Samuelson.  Abby currently works Thursdays and Fridays.



Dr Michael Wang
Michael is originally from Shanghai, China. He trained at Otago Medical School (NZ) and has recently started a career in General Practice. He is able to speak Mandarin Chinese.  Michael is interested in snow skiing and motorcycles.

Patients call him Dr Michael as his surname is pronounced ‘Wong’, to prevent being confused with Dr Chris Wong



Dr Adrian Wilson

Adrian was trained and worked in Canada before moving to New Zealand. He appreciates all aspects of being a GP but particularly enjoys working with multigenerational families and a diverse patient population. Outside of work he likes to explore his surroundings with his young family.


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Dr Verity Stirling

Verity is an Australian trained doctor. She has experience both in hospital medicine and ophthalmology prior to commencing her GP training. Her interest is in patient education and preventative medicine. Verity continues to work two half days in ophthalmology. Her hobbies include exploring the beauty of New Zealand with her young family, painting and pottery when time allows.