BACKGROUND: Deoxycholic acid (DCA) at a concentration of 10 mg/mL is commonly used for localized fat reduction, but its application in larger areas like the upper arm can lead to higher costs and discomfort. Diluting DCA may provide a cost-effective solution with reduced pain while still maintaining efficacy. OBJECTIVE: This case series aims to evaluate the efficacy, safety, and overall cost-effectiveness of diluted DCA injections at concentrations of 5 mg/mL and 2.5 mg/mL for upper arm fat reduction. METHODS: Four healthy adult females received subcutaneous injections of either 5 mg/mL or 2.5 mg/mL DCA, administered three times at four-week intervals. Arm circumference and subcutaneous fat thickness were measured at baseline and at 4, 8, 12, and 20 weeks using tape measures and ultrasonography. Pain levels and patient satisfaction were also assessed to gauge the overall balance between treatment efficacy, side effects, and costs. RESULTS: Both 5 mg/mL and 2.5 mg/mL concentrations led to significant reductions in subcutaneous fat thickness, with the 5 mg/mL group showing slightly greater reductions. However, changes in arm circumference were minimal across both groups. Pain levels were higher in the 5 mg/mL group, while the 2.5 mg/mL group experienced less discomfort. Importantly, both concentrations demonstrated a balance between efficacy and treatment cost, with the diluted solutions providing a less invasive alternative to the standard 10 mg/mL concentration. CONCLUSION: This case series represents diluted DCA injections, both at 5 mg/mL and 2.5 mg/mL, offering viable minimally invasive options for upper arm fat reduction. While the 5 mg/mL concentration shows slightly greater efficacy, the 2.5 mg/mL option may offer a more comfortable treatment experience. The choice of concentration can be tailored to patient priorities, balancing fat reduction, pain tolerance, and cost considerations.