The Consumer Price Index, which measures what consumers pay for everyday goods and services and is often looked at as an inflation barometer, jumped 5% over the last 12 months -- the largest increase since August 2008.
The index increased by 0.6% in May alone after rising 0.8% in April.
The latest data comes amid mounting inflation fears from economists. The index for all items has been trending upward every month this year.
The index for used cars and trucks increased by 7.3% in May amid a global chip shortage. The food index increased by 0.4% in May, about the same as the previous month's increase. The energy index, meanwhile, was unchanged in May.
The core index -- which reflects all items except the volatile food and energy indices -- jumped 0.7% in May, slightly less than the 0.9% increase seen in April. In the last 12 months, the core index rose 3.8% -- the largest 12-month increase since June 1992, according to the DOL.
While some levels of inflation are expected in the post-pandemic economy as demand rebounds, more data is needed to determine whether it is temporary or a more concerning, long-term trend.
Meanwhile, the DOL said in a separate statement that weekly unemployment insurance claims fell to their lowest levels since March 2020, with just 376,000 people filing jobless claims last week.
The weekly tally has been trending downwards in recent months, amid a widespread vaccine rollout and businesses reopening as pandemic restrictions ease.
The unemployment rate last month, however, was 5.8% -- still well above the pre-pandemic rate of 3.5% seen in Feb. 2020.