The present study was conducted to investigate the toxicity of potassium nitrate on glucose, cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and the possible ameliorative effect of ascorbic acid (Vitamin C). Male Wister rats are used as experimental model divided into three groups (each of 6-8 rats) and treated for six weeks as follows: Group 1: served as control; Group 2: received 2 % potassium nitrate added to the forage and Group 3: received 2 % potassium nitrate together with 1 % ascorbic acid added to rat's forage. Nitrate treatment in group 2 leads to high significant increase levels of glucose in 3rd, 4th, and 5th weeks, cholesterol level increased significantly in both 4th and 5th weeks, while ALT levels increased in the 4th, 5th and 6th weeks, and AST increased significantly in the 5th and 6th weeks. Addition of ascorbic acid with potassium nitrate, lead to reverse all the parameters nearly to normal. It was concluded that potassium nitrate causes significant toxic effect on some biochemical parameters which was ameliorated by ascorbic acid.