Blood pressure is written as two numbers: systolic (the top number, pressure when the heart beats) over diastolic (the bottom number, pressure when the heart rests). A normal resting reading for most adults is under roughly 120/80 mmHg. Many guidelines label 120-129/under 80 as elevated, and sustained readings at or above 130/80 (US) or 140/90 (UK/EU) as hypertension.
A single high reading does not mean you have high blood pressure. Pressure rises with stress, caffeine, a full bladder, talking, or a cold room. Diagnosis is based on the average of several readings on different days, often confirmed with home or 24-hour ambulatory monitoring.
If your readings are regularly above your normal range, see a doctor or pharmacist to confirm and discuss next steps. If you ever get a reading at or above 180/120 mmHg with symptoms such as chest pain, breathlessness, severe headache, vision changes, or weakness, treat it as an emergency and call your local emergency number.