The objective of this prospective study was to elucidate whether amounts of bicarbonate needed for correction of acidosis and normalization of clinical signs are influenced by blood d-lactate concentrations in calves with diarrhoea. In 73 calves up to 3 weeks old with acute diarrhoea and base excess values below −10 mmol/l correction of acidosis was carried out within 3.5-h by intravenous administration of an amount of sodium bicarbonate which was calculated using the formula: HCO (mmol) = body mass (kg) × base deficit (mmol/l) × 0.6 (l/kg). Clinical signs, venous base excess, and plasma d-lactate concentrations were monitored immediately following admission, following correction of acidosis at 4 h and 24 h after admission. The base excess and plasma d-lactate concentrations throughout the study were −17.8 ± 4.0, −0.4 ± 0.4, −3.0 ± 5.5 mmol/l (base excess), and 10.0 ± 4.9, 9.8 ± 4.8, 5.4 ± 3.4 mmol/l (d-lactate) for the three times of examination. Metabolic acidosis was not corrected in more than half of the calves (n = 43) by the calculated amount of bicarbonate, whereas the risk of failure to correct acidosis increases with d-lactate concentrations. The study shows that calves with elevated d-lactate concentrations do not need additional specific therapy, as d-lactate concentrations regularly fall following correction of acidosis and restitution of body fluid volume, for reasons that remain unclear. However, calves with distinct changes in posture and demeanour need higher doses of bicarbonate than calculated with the factor of 0.6 in the formula mentioned above probably because of d-hyperlactataemia.