Blood pressure readings are easy to take and easy to misread. These articles explain what systolic and diastolic numbers mean, why readings at home and in the clinic can differ, and what everyday factors push blood pressure up, including in younger adults.

Every blood pressure reading gives you two numbers, written as one over the other for example, 120/80. Most people know this is “blood pressure,” but far fewer understand what each number actually measures, or which one matters more.

If you’ve ever had a higher blood pressure reading at the doctor’s office than you get at home or the reverse you’re not imagining it, and you’re not alone.

High blood pressure is often thought of as a condition that mainly affects older adults.