Mastitis and lameness are 2 of the most prevalent diseases on dairy farms and increase culling risk while negatively affecting cow welfare and milk production. Identifying critical points on the lactation curve, where the first incidence of mastitis or lameness has the biggest impact on milk production, is a strategy to improve lifetime profitability and is a useful tool to help farmers make informed decisions. The aim of this study was to analyze the impact of the first incidence of mastitis or lameness on total milk production at different stages of lactation. Data were retrieved from Valacta’s database from first parity Holstein cows that calved between 2000 and 2015. After editing to ensure complete health records, the final data set consisted of 14,025 health records from 103 herds, yielding 1770 first mastitis events and 1063 first lameness events, with the remainder of records representing cows with no recorded health event (Control). First event records were grouped into transitional (1–21DIM), early (22–100DIM), mid (101–200DIM) and late (201+DIM) lactation stages to account for the most critical points of the lactation curve. Mid and late lactation cows were stratified by cumulative milk yield before the mastitis or lameness event to account for production level. Data were analyzed in a mixed model with herd as the random effect. Control cows produced 588 ± 115.6, 412 ± 130.3 and 420 ± 143.6 (P < 0.001) kg/lactation more milk than cows with the first mastitis event in transition, early and mid stage of lactation, respectively. Control cows produced 1331 ± 206.4, 803 ± 142, and 2052 ± 36.6 (P < 0.001) kg milk/lactation more than cows with a lameness event in transition, early and mid stage of lactation, respectively. Cows that reported a first case of mastitis or lameness in the late period showed no difference with the control group. These results allowed identifying long-lasting effects of mastitis and lameness on the total milk production, and therefore, could be used by farmers to make informed culling decisions to maximize both herd profitability and cow longevity.