Russia were banned from the sport in November following the first part of a World Anti-Doping Agency (WADA) report that found a "deeply rooted culture of cheating" in track and field in the country.
The nation's athletes will only be allowed to compete at the Rio Olympics if the ban imposed by the governing IAAF is lifted in time for the Aug. 5-21 Games.
"I hope if it does get to that stage that there are Russian athletes competing at the Olympics, that really drastic measures have been put in place to make sure nothing like this happens again," Briton Ennis-Hill told the BBC.
"I'd be lying if I said I wouldn't look at Russian athletes and think 'is everything 100 percent OK?'."
Ennis-Hill, who clinched gold in front of a fervent home crowd at London 2012 and claimed a second world title in Beijing last year, said she expected further disclosures in the doping scandal that has rocked the sport.
"As an athlete competing at this time, it's awful to see but at the same time you have to think that our sport has to go through this really terrible time," she added.
"It has to go to the very bottom, to the darkest place for it to then rise and come out the other side."
(Reporting by Toby Davis; editing by Tony Jimenez)
