The objective of the present study was to evaluate the consequences of 3 allowances of milk replacer (MR) during the first 2 mo of life on short- and medium-term glucose metabolism and insulin sensitivity (IS) of dairy replacement heifers. Forty-five newborn female Holstein calves (40.7 ± 4.94 kg) after receiving colostrum were randomly allocated to 4, 6, or 8 L/d of MR until 63 d of life (n = 15). A glucose tolerance test (GTT) was performed at 42, 86 and 300 d of life. Area under the curve for plasma insulin (IAUC), clearance rates of glucose (CRG) and insulin (CRI), insulin to glucose rate (ItoG), and IS were calculated. Data were analyzed using a mixed-effects model with repeated measures. There were no differences (P = 0.67) in CRG among treatments, although they decreased from 10.1 ± 0.55%/min at 42 d of age to 6.7 ± 0.56%/min at 300 d of age. Interestingly, CRI was greatest (P < 0.05) at 42 d of age, and calves fed 8 L/d had the greatest (P < 0.05) ICR throughout the study. Insulin release (measured as IAUC) after a GTT increased (P < 0.005) with age, and the increase observed between 42 and 300 d of life was more (P < 0.05) marked in calves that received 4 (from 1,000 ± 234.0 to 3,319 ± 242.7 μU/mL × 60 min) or 6 L/d (from 1,538 ± 226.1 to 3,887 ± 242.6 μU/mL × 60 min) than in those receiving 8 L/d (from 1,735 ± 226.1 to 2,940 ± 242.6 μU/mL × 60 min). The amount of MR offered had short- and medium-term effects on ItoG, with calves fed 4 and 6 L/d having lower (P < 0.05) values (145.2 ± 16.60 µU/mg) than calves fed 8 L/d (215.3 ± 16.02 µU/mg) independently of age. Insulin sensitivity tended (P = 0.07) to be lesser in calves fed 8 than in calves fed 4 or 6L/d (1.39 ± 0.04 vs 1.82 ± 0.05 mL/min x µU/mL per kg of BW, respectively). This difference was mainly due to a low IS of calves fed 8 L/d at 42 d, but as age increased, IS tended (P = 0.06) to become progressively similar among treatment groups. It is concluded that offering 4 L of MR twice daily elicits a decrease in IS and an increase in ItoG while animals are consuming MR, and the IS returns to normal values over time, but the increase in ItoG is maintained with age.