Reported and adjusted adverse events for Levaquin and it’s generic levofloxacin from 1996 through August 2019.   The FDA admits that only between 1% and 10% of all adverse events to pharmaceuticals ever get reported (1). 

Report Cases

Total Cases 42,566
Serious Cases (including deaths) 35,973
Death Cases 2,634

Adjusted Cases for 10% Reporting 

Total Cases 425,660
Serious Cases (including deaths) 359,730
Death Cases 26,340

Obviously, if the data was adjusted for 1% the numbers would be much, much higher.  From the data it is hard to extrapolate exact percentage of reporting.  It is probably variable between 1% and 10%, so, using the FDA’s admission, 10% is a conservative figure for the upper, or best, scenario.

(1) Heinrich, J. (2000, February 1). Adverse drug events: Substantial problem but magnitude uncertain. Testimony Before the Committee on Health, Education, Labor, and Pensions, U.S. Senate. United States General Accounting Office (US GAO). Available at