Anionwu began her nursing career at a young age after being inspired by a nun who cared for her eczema. At the age of 16, she left school with seven O-levels and started to work as a school nurse assistant in Wolverhampton. Later on, she continued with her education to become a nurse, health visitor, and tutor. She travelled to the United States to study counselling for sickle-cell and thalassemia centres as courses were not then available in the UK. In 1979 she worked with Dr Milica Brozovic to create the first UK sickle-cell and thalassemia counselling centre in Brent. The opening of this counselling centre pioneered the opening of more than 30 centres in the UK using the Brent Centre as a model.