If you can't remember the last time you had your blood pressure checked, make an appointment with your doctor. You can have high blood pressure for years without a single symptom. Generally, ask your doctor for a blood pressure reading at least every two years starting at age 18. If you're age 40 or older, or you're age 18-39 with a high risk of high blood pressure, ask your doctor for a blood pressure reading every year. He or she may recommend more-frequent readings if you have high blood pressure or other risk factors for heart disease.