detected conveniently by test strips using glucose oxidase methods, although these may be affected by several interferents, including ascorbate. Urinary glucose may reflect enhanced excretion because of elevated blood levels or be due to damage to the proximal tubules, where glucose is reabsorbed. Changes of hydrogen ion concentration (pH) may reflect changes in tubular function or they may simply reflect dietary protein composition. The pH of urine is a result of its cationic and anionic composition and will be influenced by any substances that perturb the excretion of individual ions, including hydrogen ions. The products of normal metabolism produce an excess of acid substances, which are buffered by a bicarbonate system in the kidney. Urine samples from dog and man are usually acid, containing ammonium ions, due to processes of ionic changes that occur in the distal region of the nephron and also reflecting the nature and composition of the diet being consumed. e.g. rotein content