Why is my blood pressure suddenly higher?

Various causes. Cannot answer in your case; i cannot interview you/perform exam.Generally, blood pressure (BP) can rise despite treatment from emotional stress, physical activity prior to BP check, use of over-the-counter medications like oral decongestants, higher salt in diet (soup, canned food, lunch meat, cheese, snacks, frozen meals etc), increased weight, caffeine, sleep apnea, frequently unidentified cause.