Providing insufficient lysine to lactating sows can reduce piglet performance and subsequent farrowing performance of sows. Current SID lysine and ME recommendations for lactating sows are approximately 60 g/d and 20 Mcal/d, respectively. Because of variations in feed intake during lactation, a portion of sows do not meet recommended Lys intake levels. There is no clear understanding of the Lys:Calorie ratio when dietary energy is increased in the summer to ensure adequate caloric intake. The objective was to evaluate a potential advantage of feeding diets with SID Lys and energy levels that exceed recommendations to lactating sows. A total of 855 sows were fed during the summer of 2023 in 2×2 factorial arrangement of treatments in a randomized complete block design. Factors included SID lysine [low (0.85%) vs high (1.11%)] and ME [low (3,183 kcal/kg) vs high (3,334 kcal/kg)]. Diets were formulated to deliver 61 g of SID lysine at 0.85% inclusion to sows that consume 7.2 kg of complete feed per day. Primary outcome variables were sow body composition, lactation ADFI, average piglet weaning weight, and pre-wean mortality. There were no interactions between treatments (P>0.05). SID Lys intake was 61.2 and 76.4 g/d for low and high Lys, respectively (P< 0.01). ME intake was 21.9 and 23.4 Mcal/d for low and high energy, respectively (P< 0.01). Contrary to expectations, ADFI did not differ (P=0.25) between sows fed the low- and high-energy diets, however, sows fed low lysine consumed 0.29 kg more feed (P< 0.01) per day compared with sows fed high lysine. There were no differences (P≥0.70) in the number of piglets born alive for any treatment group. Sows fed high energy had 0.27 fewer (P< 0.01) still-born piglets per litter compared with sows fed low energy. Pre-wean mortality was also reduced (P=0.05) by 0.76 percentage units in litters of sows fed the high-energy diet compared with litters of sows fed the low energy. Lysine level had no effects on farrowing and litter performance (P>0.05). Litters from sows fed the high-energy diet gained 1.2 kg more (P=0.05) weight during lactation and tended to result in litter-weaned weights that were 1.5 kg heavier (P=0.06) than litters from sows fed the low-energy diet.