The results of the tests are included in a final report by state Chief Medical Examiner Dr. H. Wayne Carver II that has been turned over to Connecticut state prosecutors, The Hartford Courant reported Monday.
The tests did not find any traces of alcohol, illegal drugs or anti-psychotic or antidepressant drugs.
The absence of drugs in Lanza's body indicated that "something else" made him commit the murders, said Dr. Michael Baden, the former chief medical examiner for New York City.
The findings did not surprise former FBI profiler Mary Ellen O'Toole.
Shooters in other recent killings also tested clean for drugs, she said, because they wanted a "clear head" during the attacks.
A final report on the police investigation of the shootings should be released by the end of June, Danbury State's Attorney Stephen Sedensky said.
2014: The Year in Music [PHOTOS]