The aim of this study is to assess the practice of heparin administration in real-life situations. This study was conducted at the coronary care unit (CCU) in one of the busiest hospitals in Kuwait; with special attention to the rate of heparin resistance, potential factor that may predict resistance or responsiveness and heparin related complications. A prospective observational study was conducted in Farwania hospital over a 4-month period; this study included 146 patients admitted to the CCU. Patients were treated with UFH according to a standard normogram. Several variables were collected and analyzed, including demographic data, initial diagnosis, activated partial thromboplastin time (APTT) on admission and at 6, 24, and 48 h after UFH administration, and any complications that occurred. A significant number of patients had subtherapeutic APTT at 6, 24, and 48 h (41.1%, 42.3%, and 46.7%, respectively). There were four factors that predicted heparin resistance, including race, gender, admitting diagnosis (unstable angina vs. acute myocardial infarction), and an APTT ratio of less than one on admission. There was no significant difference in the rate of development of complications among different groups. Heparin resistance is a common phenomenon especially in the first period of heparin therapy. Special attention should be given to some groups like females, patients admitted with unstable angina, and those with APTT below the normal range. Evidence based protocols for heparin administration and monitoring must be adopted to prevent the risk of under or over anticoagulation.