The survey findings were based on more than 14,700 interviews of U.S. adults from April 1 to 30 as part of the Gallup-Healthways Well-Being Index.
The downward trend in those uninsured coincided with the introduction of online health insurance marketplace exchanges last October as part of the Affordable Care Act. The original March 31 deadline was extended to April 15 for those who had already begun process of buying health insurance.
The uninsured rate was lower in April across nearly every key demographic group, but it dropped most among blacks, falling 7.1 percentage points to 13.8 percent. The number of uninsured among Hispanics dropped 5.5 percentage points since the end of 2013, but the demographic still has the highest uninsured rate at 33.2 percent.
The uninsured rate among lower-income Americans earning less than $36,000 a year dropped 5.5 percentage points to 25.2 percent, since the fourth quarter of 2013.
The survey's margin of error was 1 percentage point.