That number is even higher for those delaying treatment for a serious condition, which has jumped since the early 2000s, while the amount of those putting it off for a non-serious condition has barely budged.

And uninsured Americans are more than twice as likely as those who have Medicare, Medicaid or private insurance to admit they put off medical treatment. Well over half (59 percent) of the uninsured have done so, compared with roughly one-quarter of those with Medicare or Medicaid (22 percent) or private health insurance (25 percent).

Additionally, younger Americans, aged 18 to 29, and lower-income Americans — two groups the least likely to have coverage —"are significantly more likely to have put off treatment than their older and higher-income counterparts."

A little more than a decade ago, the percentage of people putting off treatments was 19 percent, according to Gallup.

"One possible explanation for the higher numbers since then is the increase in the number of high-deductible plans," Gallup researchers said. "Americans with serious conditions who have insurance may be putting off treatment to avoid high out-of-pocket costs."

Though there's the chance PPACA can help alleviate this issue, Gallup researchers said, a new HealthPocket report found Obamacare plans offer much higher deductibles than earlier ones, suggesting more people might put off or skip treatment now.

Additionally, Gallup said, the possible uptick in the number of Americans seeking medical treatment under PPACA "may put additional strain on the health care system, creating new problems."