Crengle graduated in medicine from the University of Auckland in 1985. She notes that there were three other Māori students in her class, whereas nowadays a typical cohort might have fifty. She then completed a master's degree titled
Mā Papatuanuku, ka Tipu ngā Rākau: a case study of the well child health programme provided by Te Whānau O Waipareira Trust in 1997, supervised by
Fiona Cram. She then completed a
PhD titled ''The management of children's asthma in primary care: Are there ethnic differences in care?'' at the
University of Auckland. Crengle then moved to the
University of Otago, rising to full professor. She resides in Invercargill, where she practises one day a week. Her research focuses on issues of inequity in the health system, where she says some metrics are getting worse, such as the percentage of Māori women participating in cervical screening. She also teaches in public health and Māori health at the university. In 2021 she was appointed to the
Māori Health Authority as part of the reformation of the health system. She said "It's exciting that there's such an explicit focus on equity and improving Māori health outcomes across the whole reform." == Selected works ==