There is a growing concern that nursing students struggle to retain adequate physiological knowledge throughout their program to meet their entry to practice competencies. However, how much and what knowledge is lost and when this occurs over a four-year undergraduate Bachelor of Science in Nursing program remains to be evaluated. Moreover, physiological knowledge retention has not been studied as extensively as anatomical knowledge retention in health care disciplines, including nursing programs (Narnaware, Y., 2021). Most of these studies are conducted after graduation (Aari et al., 2004) or focused on very limited systems (Pourshanazari et al., 2013). The present study aims to evaluate the level of physiological knowledge loss by nursing students in the fourth year between completing their physiology course in first-year nursing and fourth-year Critical Care nursing course . To evaluate physiological knowledge loss in the fourth year, nursing students were quizzed on ten organ systems using the online quizzing platform- Kahoot. Approximately nine to eleven knowledge and comprehension-level multiple-choice questions were delivered via kahoot. Then, these scores were compared to first-year quiz scores on the same content to determine overall knowledge loss over three years. Using SPSS II, the data was analyzed, and means were compared using 2-sample t-tests. The scores are described for each organ system by reporting the mean and standard deviation (±SD) with statistical significance set at P < 0.05 for all tests. The mean score of questions from all organ systems in year one was 62.89 ± 10.49 (±SD). Comparing that score to matched test items evaluated in the Critical Care course, there is a decrease in the overall mean score from 62.89 ± 10.49 (±SD) to 47.69 ± 8.23 (±SD). This equates to a 15.2% knowledge loss or 84.8% retention rate within three years. Organ-specific knowledge loss was highest for fluid and electrolytes (30.7%), hormones (28.6%), defences (22.5%), and reproductive physiology (22.5%), followed by renal physiology (19.7%). Knowledge loss was comparatively lower for blood (15.9%), inflammation (11.2%), vascular (7.5%) and respiratory physiology (4.7%). However, this loss was lowest for digestive physiology (-3.7%). The results of this study demonstrate a lower level of knowledge loss overall, with variations in loss being system-specific. The level of knowledge loss in the present study was significantly lower than previously reported in medical and allied health students (Pourshanazari et al., 2013) and lowest than anatomical knowledge retention levels in the same population (Narnaware and Neumeier, 2021). However, compared to the third year, knowledge loss in the fourth year is not significantly different (Narnaware et al., 2021). Applied for Teaching Physiology Section- Travel Fellowship Award. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.