Quest Diagnostics is one of the two largest clinical laboratory testing companies in the U.S., processing roughly 244 million test requisitions annually alongside primary competitor LabCorp. Quest collects specimens from patients at its ~2,400 patient service centers or physician office locations, transports them across a national logistics network (83,000+ stops per day), runs diagnostic tests, and delivers results electronically — typically integrated directly into the ordering physician's EHR. Quest serves roughly half the physicians and half the hospitals in the U.S. annually. The core business, Diagnostic Information Services, accounts for 95%+ of revenue and spans routine testing (blood panels, urinalysis), esoteric testing, and a growing advanced diagnostics portfolio in oncology, neurology, autoimmune, and women's health. Quest earns revenue on a fee-for-service basis, with most payment coming from health plans and government programs rather than patients directly. Revenue growth is driven by requisition volume, tests per requisition (now exceeding 4.2, up from ~3.5-4.0 pre-COVID), and test mix shifting toward higher-value advanced diagnostics. Quest's consumer channel (~$250M, growing >20% annually) is a fast-growing, cash-pay business operating through QuestHealth.com and wellness partnerships with WHOOP, Oura, and Function Health. The hospital channel includes both reference testing and a growing lab management offering (CoLab) where Quest operates hospital lab operations directly. Quest's cost structure carries significant operating leverage, and Quest targets 3% annual cost savings through lab automation, logistics optimization, and AI productivity initiatives.