The aim of this study was to induce acute metabolic acid/base changes of ≥ 2 mequiv ˙ l-1 change in base excess (BE) to aid future investigations of respiratory parameters under these conditions. Ammonium chloride (NH4Cl) was administered to induce acidification and furosemide was used to induce alkalization. Nine healthy volunteers (six men and three women aged 35 ± 18 years) ingested a calculated amount of NH4Cl at t = 0 and a repeat dose after 60 min. Eight healthy volunteers (three men and five women aged 37 ± 16 years) consumed 40 mg of furosemide. Arterialized capillary blood gases were measured at t = 0, 30, 60, 90, 120 and 180 min. In the case of acute metabolic acidosis, the target acidification of 2 mequiv ˙ l-1 was attained after 30 min and the greatest change was achieved at 90 min: -4.9 (2.2) mequiv ˙ l-1. In the case of acute metabolic alkalosis, the target alkalization of 2 mequiv ˙ l-1 was reached between 120 and 180 min and the greatest change was seen at 180 min: +2.2 (1.4) mequiv ˙ l-1. Significant (P < 0.05) changes in acidification compared with baseline BE values were found between 60 and 180 min; significant (P < 0.05) changes in alkalization were found between 120 and 150 min. Paco2 did not change significantly in either condition. We conclude that NH4Cl and furosemide induce a steady state of pure metabolic acid/base conditions in humans, which is buffered in an isocapnic manner.