Numeracy skill level of patients has great influence on their preferences and priorities for the treatment options concerning their healthcare. Not properly numeracy-assessed patients are prone to make inaccurate and inappropriate decisions for their medical treatments. There are many challenges that the researchers face in designing and developing patient-sensitive numeracy assessment methods. The adaptability of the numeracy assessment is considered to be one of the most important issues to address. In this paper we propose a goal-driven confidence-based model for patient numeracy assessment (C-PNA) adaptable to each individual patient. The model is empirically validated in a case study.