The crypto-currency dropped in value from $47,000 (£34,700) earlier this week to less than $42,000 (£31,000) per digital coin.
It follows minutes from a meeting of the Federal Reserve, which suggested it may raise interest rates.
Political events in Kazakhstan have also raised concerns about the network's capacity.
Because of its global and decentralised nature, attributing a rise or fall in the price of Bitcoin to a single cause is difficult. But many commentators have pointed to the release of the Federal Reserve's December meeting notes as one factor.
