This thesis aims to investigate the relationship between increased protein dosage intake and selected haematological and biochemical markers. An experiment was designed using the Wistar laboratory rats of the male gander and similar age (born within +/- 5 days). These specimens were then divides into 3 groups with 10 specimens each. The age of the specimens at the beginning of the experiment was around 62 days. The first group was fed the standard corny mixture ad libitum, while the second group received 6 grams of the standard corny mixture and 10 grams of beef meat per day (thus reflecting the same amount of nitrous compounds as for the first group) and the last (third) group was fed ad libitum with homogenised beef meat. Before the diet was imposed on the three groups, blood samples were collected from all specimen from the lateral tail vein; after the diet was completed, blood samples were collected by in vivo heart puncture. All blood samples were subjected to haematological (using EDTA blood) and biochemical (using blood plasma) analysis. Overall, the following markers were measured: amount of erythrocytes, haematocrit level, haemoglobin level and Mean Corpuscular Volume (MCV) for the haematological analysis and triacylglycerol level, cholesterol level, amount of urea, amount of magnesium and the amount of iron for the biochemical analysis. Dietary induced significant changes were observed for the following markers: number of erythrocytes, levels of haemoglobin and MCV from the haematological analysis and cholesterol levels, amount of magnesium and amount of iron from the biochemical analysis; therefore showing that altered diet can have affect haematological and biochemical blood markers.