Exactly one month has passed since the NFL instituted blood testing for human growth hormone — a test experts say is almost impossible to fail.

An AP analysis of the testing protocol approved by the league and the NFL Players Association after more than three years of wrangling found that only the most reckless or uninformed player would seem to have a chance of getting caught using HGH.

Of nearly 2,800 HGH tests from various sports analyzed last year at labs accredited by the World Anti-Doping Agency, zero turned up positive.

Says Travis Tygart, the CEO of the U.S. Anti-Doping Agency: “You pretty much have to be a fool to test positive” at a team facility.

NFLPA spokesman George Atallah says: “There are always things that can be worked out or need to be improved, but generally, it’s working like it’s supposed to.”