Currently both doses for what is known as an early medical abortion, and what is sometimes called an "abortion pill," must be taken at a hospital or other medical premises.
Abortion provider the British Pregnancy Advisory Service argues medical advances mean it is safe to allow the second dose to be self-administered. It says that is the case in the U.S., France and Sweden.
The government opposed the change. High Court judge Michael Supperstone on Monday rejected the advisory service's legal challenge.
There are about 70,000 early medical abortions during the first nine weeks of gestation in Britain each year.