The purpose of this quadruple-masked, randomized-controlled study is to study the treatment of urgency urinary incontinence (UUI) specifically among older women with low- versus standard-dose of onabotulinumtoxinA (BTX) via: symptom-specific and health-related quality of life (QOL; Aim 1), patient-reported and clinical outcome measures including adverse events (Aim 2), qualitative experience with focused interviews (Aim 3) and cost burden and economic impact (Aim 4). This study is an active collaboration between researchers in Gynecology, Urology, and Geriatrics at Dartmouth Hitchcock Medical Center (DHMC) and at 6 other centers; University of Alabama (UAB), University of Pittsburgh (U Pitt), University of Texas Southwestern (UTSW), Kaiser Permanente of Southern California (KPSCP), Oregon Health & Sciences University (OHSU), and University of Nebraska Medical Center (UNMC; joined January 2025). The investigators also have collaborators at Stanford University and University of Connecticut, though those sites are not recruiting participants.