A senior nurse in Whangarei who challenged the legality of taking a blood sample from her foot for alcohol testing will be sentenced on one charge of drink driving tomorrow.

Karen O'Keeffe had challenged a drink-driving charge laid after a blood sample was taken from her foot at the Whangarei police station on November 28, 2014.

O'Keeffe returned a reading of 104 milligrams of alcohol per 100 millilitres of blood - twice the legal blood limit of 50 milligrams for drivers aged 20 and over.

She was found guilty after a judge-alone trial in Whangarei District Court last month.