If you noticed higher prices at the supermarket and gas station last month, you're not alone.

The consumer price index rose 0.3% in September, less than the 0.4% increase in August, the Labor Department said Wednesday. Excluding food and energy, so-called core prices increased 0.1%, the smallest increase since March.

But if you're a consumer, of course, food and gas prices matter. Food prices rose 0.4% in September, pushed up by big increases in dairy, cereals and fruits and vegetables. Gas prices rose 2.9%. Costs of medical care, airline fares and tobacco also increased.

Dairy prices have jumped 10.2% in the past year. Gas prices have soared 33.3%. Those increases are big reasons why inflation has jumped 3.9% in the 12 months ending in September -- the largest year-over-year increase in three years. 

The annual increase in consumer prices means that 55 million Social Security beneficiaries will receive higher benefits next year. They will get a 3.6% cost-of-living increase, the first since 2009. That's because Social Security checks are tied to the consumer price index.

There was some good news in the September report. Apparel prices declined after a series of sharp increases, and prices for used cars and recreation fell. New-vehicle prices stayed flat.