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.
The minutes suggest that America's central bank might raise interest rates sooner than some had anticipated, and sell off some of its assets.
That could have led to a knock-on effect of traditional investors who hold Bitcoin, as they pursue less risky assets instead.
At the same time, a huge amount of the world's Bitcoin mining - the process by which transactions are verified and new "coins" made - takes place in Kazakhstan.
The massive Central Asian country has been hit with political unrest this week, as citizens took to the streets to protest against rising fuel prices. Fatal violence followed as demonstrators - which the country's leaders paint as "rioters" - seized buildings in the largest city, Almaty.