Introduction: Because there are increasing insulin therapies currently used in diabetes treatment, patients’ injection technique and knowledge are more important than before. Therefore, this study is conducted to investigate the relationship between patients’ education, level of cognition, and insulin usage in Taiwan. Method: A cross-sectional survey is conducted. A questionnaire regarding injection technique is answered by 88 diabetes patients from a hospital in New Taipei City. Results: (1) There is a statistical difference between patients’ education, provided by different health care professionals, and their level of cognition (p=0.003). That is, patients’ level of cognition is higher when education is provided by certified diabetes educators and professional in-patient registered nurses. (2) There is a positive correlation between levels of cognition and patients’ behaviors. Patient behavior includes washing hands before injection (p<0.001), sterilizing injection sites with alcohol before injection (p=0.028), rotating injection sites (p=0.004), changing a new needle before injection (p<0.001), frequency of changing needles (p<0.001), timing of needle removal (p=0.009), and dwell time after injection (p<0.001). (3) Other factors that affect the consistency between cognition and behavior include the age of patients, whether or not they are living alone, patients’ degree level, and the timing of insulin usage. Conclusion: If patients have enough time and space to receive patient education by diabetes educators and in-patient nurses, they show a higher cognition score. However, there seems to be no consistency between level of cognition and behavior in patients who are younger, live alone, are well-educated, and are newly prescribed insulin.