Serum starvation is a widely used condition in molecular biology experiments. Opti-MEM is a serum-reduced media used during transfection of genetic molecules into mammalian cells. However, the impact of such media on cell viability and protein synthesis is unknown. A549 human lung epithelial cell viability and morphology were adversely affected by growing in Opti-MEM. The cellular protein levels of chloride intracellular channel protein 1, proteasome subunit alpha Type 2, and heat shock 70 kDa protein 5 were dysregulated in A549 cells after growing in serum-reduced media. Small interfering RNA transfection was done in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum, and knockdown efficacy was determined compared with Opti-MEM. Similar amounts of knockdown of the target proteins were achieved in DMEM, and cell viability was higher compared with Opti-MEM after transfection. Careful consideration of the impact of Opti-MEM media during the culture or transfection is important for experimental design and results interpretation.