Mabel (Mēpara) Te Aowhaitini Mangakāhia was born on 4 September 1899 at Whangapoua on the north-eastern coast of the Coromandel Peninsula. She was the youngest of four children of Hāmiora Mangakāhia and his third wife, Meri Te Tai. Through his mother, Hāmiora Mangakāhia was a high-ranking member of Ngāti Whanaunga; his hapū were Ngāti Hei and Ngāti Pare. His father was from Ngāti Kahungunu. Meri Te Tai was from a family of ruling Te Rarawa chiefs from Panguru, Hokianga; her hapū were Ngāti Te Reinga, Ngāti Manawa and Te Kaitūtae. Mabel was exposed to parental role models of competent leadership and responsibility from an early age. Hāmiora had been premier of the Kotahitanga parliament in the 1890s and was still promoting the movement in 1907: Meri Te Tai Mangakāhia was a leader of the women's movement within Kotahitanga.
Mabel Mangakāhia was brought up at Whangapoua and attended a local primary school. Meri Te Tai took a tremendous pride in her family, and Mabel's childhood was happy and secure. As a teenager she was sent to Auckland Girls' Grammar School, and then to Queen Victoria School for Māori Girls, where she did well academically and won a nursing bursary. She did her general training in Auckland Hospital, completing it in 1923. Initially Māori nurses had followed a special, less rigorous course of training, but that had been abolished in 1913; the course taken by Mangakāhia was that prescribed for any aspiring professional nurse.
In June 1925 she was appointed to Rāwene as assistant district health nurse for Hokianga. The Department of Health expected Māori to be assistants to Pākehā nurses until the necessary experience to manage a district had been acquired. Mangakāhia was assistant to Ella Leslie, an efficient and ebullient character. Since Leslie owned a Dodge, it was not often necessary to ride on horseback or bicycle as was customary in making visits to remote settlements, but their cottage was ‘tumbled-down and damp’. The work was hard; district nurses were called on at all hours of the day and night to attend the sick, often having to contend with bad roads and flooded rivers. They gave health talks in schools, and taught their patients hygiene and good health practices by practical demonstration rather than theoretical explanation. In the late 1920s Mabel Mangakāhia was one of only three or four active, qualified Māori district nurses serving Māori communities.
In 1928 Mabel Mangakāhia took a midwifery course at St Helens Hospital, Auckland, and in July 1929 was transferred to be a district nurse there. In November that year she was seconded for her Plunket training at Karitāne-Harris Hospital, Dunedin. In 1930 she was transferred to Tokaanu, the isolated new centre for the vast Taupō district, which stretched from Kapua Mill and Ōtoko to Taupō and Mōkai. She was provided with a cottage by the Health Department, which also paid for a Māori assistant. The Tūwharetoa Trust Board contributed generously towards the upkeep of their nurse, including provision for transport by taxi. In December 1930 the nurse instructor, Mary Lambie, reported to the department that Nurse Mangakāhia's drug cupboard and equipment were well kept and that she was visiting and giving health instruction to pupils at eight schools. She recommended that she use a service car rather than taxis to save money.
After a short period relieving in Ōtaki, Mabel Mangakāhia returned to Tokaanu. In the early 1930s she was the pioneer district nurse of Te Araroa near East Cape. In 1936 she was appointed district health nurse in Hamilton. The two district nurses there were expected to cover a huge area with a Māori population of approximately 13,000; subsequently three more nurses were appointed at Kāwhia, Morrinsville and Te Kūiti. The district nurses lived in boarding houses, and stored equipment in their own rooms, where they treated patients. When there was disagreement between the Health Department and the Waikato Hospital Board over the amount of subsidy the board should contribute towards the upkeep of the district nurses, H. B. Turbott, medical officer of health, reminded the board that the district nurses were treating many Māori in their homes who would otherwise require treatment at the hospital.
In February 1939 Mabel Mangakāhia was granted leave and a bursary from the Health Department to attend the postgraduate course in Wellington. She was probably the first Māori to complete this. She returned to Hamilton, but early the following year was diagnosed with cancer. She died in Hamilton, aged only 40, on 23 August 1940. She was taken home, and on 25 August was buried at Whangapoua.
Mabel Mangakāhia had never married. The most eminent and successful Māori nurse of her day, she remained wedded to her profession despite attempts by her family to arrange marriages for her. She often returned to Whangapoua for visits and holidays, and her nieces and nephews remembered the malt she gave them for their health, and the fun they had with her, including picnics and expeditions to collect pine cones. Although she had no direct descendants, her dedication to her profession meant that she had ‘children’ all over the country.