Wholesale prices for gas and food shot up in September, making it the most expensive month for companies since May.

The Labor Department says the Producer Price Index rose 0.8 percent last month due to food and energy costs.

Excluding energy prices, wholesale prices rose just 0.3 percent.

Although gas prices began to drop toward the end of September, it was too late to have any real effect on inflation rates for the month.

Economists said seasonal adjustments magnified the rise in energy costs.

"Inflation is not wildly out of control, but it certainly isn't as tame as would be expected during this stage," said Jennifer Lee, a senior economist at BMO Capital Markets.

A small amount of inflation is good for the economy, according to economists. It encourages businesses and consumers to spend and invest money sooner rather than later.