According to the development of medical information systems, shortened examination time per patient could increase the number of treatments, resulting in the rapid growth of the amount of medical data. Studies on how to efficiently compress and store medical text data of increasing patients are in progress. However, previous methods have the shortcoming of compressing medical text data as it is, resulting in low compression rate. This research tries to overcome the problem by using the gamma coding method which enables compression in bit unit. We propose a new compression scheme which encodes the deviations between measured values and normal range values. Furthermore, we suggest to use the previous value with the least deviation from the measurement as the standard value to encode that deviation. Even though the suggested methods are simple, they have high compression rates. Through performance evaluation, we show that the suggested methods are more efficient than the previous methods.