The ph of human blood is maintained at around ph 7.4. why does a buffer system need to be present in blood to protect against changes in ph due to increases in acids? the ph of human blood is maintained at around ph 7.4. why does a buffer system need to be present in blood to protect against changes in ph due to increases in acids? adding bases doesn't alter the ph of most solutions significantly. the metabolic processes of the body produce more acids than bases. our blood is not exposed to any bases. under normal conditions, only acids need to be buffered.