I have a bottle of 5 mg glipizide tablets that i forgot to use. bottle says use before 7-27-18. are they still safe to use?

Probably OK: Drug expiration dates are very arbitrary -- they mean only the drug's effectiveness and side effects haven't been tested after a longer time. If properly stored and not overheated, like in a car's glove box, almost certainly it's still effective with no increased risk of side effects. Anyway, this may be an arbitrary date, a year after the prescription.