Tranexamic acid reduces trauma mortality in CRASH-2 (20,211 patients) — but only within 3 hours of injury. This 2026 guide covers the complete mechanism, all indications with dosage table, the 3-hour timing rule that changed emergency medicine globally, thrombosis risk with the OCP, colour vision warning, FDA-approved menorrhagia dosing, and how it treats melasma through a unique plasminogen pathway.