Francesca Palmer-Norris is anxiously awaiting results of the hospital tests after she was pricked by the needle on the top deck of a bus in Brighton, East Sussex.
The student says her 'head is all over the place' after she spent four hours in hospital where she was given a hepatitis jab and had blood tests.
Francesca told her local paper: "My friend and I had got on the bus to go home and we were sat on the top.
"I suddenly had this shooting pain in the back of my leg. I reached down and pulled out a needle that had snapped in half.
"Then I looked down the side of the bus seat and there were packets and a syringe on the floor and the rest of the needle."
She added: "When the bus reached the next stop, I explained to the driver what had happened and he said it was best to go to the hospital."
She was given a jab and had blood tests before going home that night.
Francesca said: "The worrying thing now is I am waiting for the results to come back.
"My head is all over the place - I can't sleep."
Adrian Tullett, head of operations at the bus company, said the incident was being investigated using CCTV footage.
He added: "The driver followed procedure and secured off the top deck as soon as he was made aware of an object that needed removing from the seating area.
"He took the vehicle out of service for a full inspection as soon as was practically possible.
"We would like to reassure passengers we take these matters very seriously and that all our buses get a visual inspection at the end of each journey. Our customer services team is liaising direct with the girl's family."
Sussex Police is also investigating the incident.