Clinical presentation helps differentiate between upper and lower urinary tract infections (UTIs). UTIs are classified as either complicated or uncomplicated. A complicated UTI is associated with an underlying condition that increases the risk of failing therapy. Primary laboratory tests for UTIs consist of urinalysis and urine culture. The most common pathogen for uncomplicated cystitis and pyelonephritis is Escherichia coli. Nitrofurantoin, fosfomycin, and trimethoprim-sulfamethoxazole are first-line therapies for acute uncomplicated cystitis. Decisions regarding antibiotic agents should be individualized based on patients' allergies, tolerability, community resistance rates, cost, and availability.