Introduction: When blood is stored in liquid medium, the red cells undergo a series of biochemical and structural changes that have major influences on their viability and function after transfusion. These changes are known as the storage lesion. The aim of this study was to evaluate various biochemical changes in CPDA–1 stored whole blood at 4 0C over a period of 35 days. Material and Methods: The present study was a prospective study carried out in the Department of pathology, S.S Medical College Rewa on 50 healthy voluntary donors who donated blood in the blood bank of SS medical college. Each sample was analysed for following biochemical parameters– serum albumin, Total protein, serum sodium and potassium on day 1,7,14,21,28 and 35. Result: In the present study mean value of potassium increased within the period of 7 days and continued subsequently. Sodium on the contrary slightly reduced. Mean value of serum albumin reduced from 3.72gm/dl on day one to 2.64gm/dl on last day. Total serum protein also show slight reduction. Conclusion: Current evidence shows that metabolic, biochemical, and molecular changes occur during the storage of blood products and that these changes may lead to harmful consequences in the recipient.