It doesn't become dangerous, once expired, but it may start to lose effectiveness. If it is in a bottle as dispensed from you pharmacy, it would have expired a year from the date it was dispensed. If it's that old, my suggestion would be best to dispose of it and obtain a new supply, if you still need this medication.

However, on the contrary, according to Harvard University’s Medical Center, “Most of what is known about drug expiration dates comes from a study conducted by the Food and Drug Administration at the request of the military. With a large and expensive stockpile of drugs, the military faced tossing out and replacing its drugs every few years. What they found from their study is that 90% of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date. So, the expiration date doesn't really indicate a point at which the medication is no longer effective or has become unsafe to use. While it's true that the effectiveness of a drug may decrease over time, much of the original potency still remains even a decade after the expiration date.”

Ref: health.harvard.edu/staying-healthy/drug-expiration-dates-do-they-mean-anything

Hopefully this info can help you make an informed decision when it comes to your medication.