Oil is far below the record of $147 a barrel reached in July.
Oil prices have fallen below $50 a barrel for the first time since May 2005 amid fears of a recession and expectations that demand will drop.
US light sweet crude fell to $49.62, while London-traded Brent crude fell to $48.90 a barrel.
The price of oil is around two-thirds cheaper than in July, when it hit a record above $147 a barrel.
Members of oil cartel Opec are to meet on November 29, after opting to cut output by 1.5 million barrels per day.
"The lack of any positive news on the demand front as well as continued global economic turmoil continues to result in a dearth of bullish news," said Jonathan Kornafel, Asia director of Hudson Capital Energy.
On Wednesday, the Federal Reserve said it expected the US economy to shrink in the first half of next year, adding to fears over lower demand for fuel.
Figures from the Energy Information Administration released on Wednesday showed US stocks of crude oil increased by 1.6 million barrels last week - twice as much as expected.
Meanwhile figures from Japan showed the country experienced its second trade deficit in three months in October, with exports 7.7% lower year-on-year.
Amid signs of the wider slowdown, investors and hedge funds have been turning to cash, and away from commodities.