Immunoactivation via a lipopolysaccharide (LPS) bolus elicits well-characterized immune and metabolic responses. However, acute LPS injections likely do not mimic chronic on-farm immunoactivation. Therefore, experimental objectives were to characterize metabolic responses to continuous LPS infusion in lactating Holstein cows (164 ± 22 DIM; 676 ± 16 kg BW; parity 3.1 ± 0.4). Following 3 d acclimation, cows were enrolled in 2 experimental periods (P). Period P1 (3 d) served as baseline for P2 (7 d) during which cows received 1 of 2 treatments: (1) saline-infused and pair-fed (CON-PF; i.v. 40 mL saline/h; n = 5) or (2) continuous LPS-infused and ad libitum-fed (LPS-AL; E. coli O55:B5; 0.017, 0.020, 0.026, 0.036, 0.055, 0.088, and 0.148 µg/kg BW/h for d 1–7, respectively; n = 6). Pair-feeding was utilized to eliminate confounding effects of dissimilar nutrient intake. Blood samples were collected on d 1 and 2 of P1 and d 1, 3, 5, and 7 of P2. LPS reduced DMI (28%) on d 1 but DMI gradually returned to pre-infusion levels by d 6. Overall milk yield was reduced similarly (17%) between treatments. There were no differences in circulating glucose (P = 0.42). Plasma insulin was increased 140% in LPS-AL relative to CON-PF cows (P = 0.01). Circulating nonesterified fatty acids were increased from d 1 to 3 and subsequently decreased from d 3 to 7 in both treatments (P < 0.01). Relative to P1, CON-PF cows had a 29% decrease in plasma β-hydroxybutyrate (BHB; P = 0.04) while BHB in LPS-AL did not change (P = 0.40), thus LPS-AL cows had overall increased (41%) BHB relative to CON-PF cows (P = 0.01). Blood urea nitrogen (BUN) gradually decreased in CON-PF cows and it increased in LPS-AL cows from d 1 to 5 (P = 0.04), resulting in an overall 25% increase in LPS-AL versus CON-PF cows (P = 0.02). In conclusion, continuous LPS infusion increased insulin, BHB, and BUN relative to CON-PF cows. Increased insulin is characteristic of both acute and chronic LPS models; however, chronic LPS infusion increased BUN and BHB; which is distinct from acute models and may indicate increased muscle proteolysis and altered carbohydrate/lipid metabolism.