The objective of this study was to assess the effect of ketosis status on behavioral activity in transition dairy cows. A total of 1,024 Holstein dairy cows (390 primiparous and 634 multiparous) in 3 commercial dairy herds were enrolled at 14 d before calving until 14 d post-calving. Monthly, a cohort of 20 to 36 cows was enrolled at each farm and electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) were fitted to the hind leg of individual cows to assess their lying time. Holstein animals were screened for NEFA at 7 d prepartum (dpp), calcium at calving (Ca), ketosis (KET) at 7 ± 3 and 14 ± 3 DIM by measuring β-hydroxybutyrate (BHB) in serum samples, and haptoglobin at 7 ± 3. A case of KET was recorded when lactating cows had serum concentration of BHB ≥1.2 mmol/L. Cases of retained placenta, milk fever, metritis, pneumonia, digestive disorders, and mastitis during the study period were recorded. Lactating cows were allocated into 1 of 4 groups: (1) non-disease (ND, n = 613; cows without KET and any other health conditions), (2) cows with only KET (n = 152), (3) sick cows experiencing ≥1 health conditions, but without KET (SICK, n = 198), or (4) cows with KET plus at least 1 health condition (KET+H, n = 61). Data were analyzed using MIXED procedure of SAS. Multiparous cows had greater LT (P < 0.0001) compared with primiparous cows, regardless of health status. Cows experiencing KET+H had increased LT (~1 h; P < 0.05) compared with ND cows for the first 6 DIM after parturition. Cows experiencing KET, KET+H or SICK had increased NEFA prepartum (P < 0.0001) with greater BCS loss early in lactation (P < 0.0001), reduced Ca (P = 0.004), and increased HAPTO (P = 0.0002) compared with ND cows. These results suggest that LT along with energy and Ca balance are critical for transition cow health.