The 19-year-old singer was due to perform in Nottingham on Saturday, but she pulled out and postponed the concert. She also cancelled her scheduled gig in Bournemouth last Tuesday.
The 'Umbrella' hitmaker was due to play Birmingham's NEC Arena tonight but her doctor advised her to not go through with the show.
A representative from the NEC said that Rihanna "appreciates the love and support of all her fans and wants nothing more than to see and connect with them".
The reason for the doctor's order has not been confirmed.
Rihanna started her European tour in Paris last month and was due to finish on December 21 in Russia.