How do I know if I have high blood pressure or hypertension?

Answer: To know if you have high blood pressure or hypertension, you need to know the definition of hypertension.

Most of the time, hypertension is picked up by physical exam because it does not show any symptoms until it is very advanced or severe. In order to know the definition of hypertension, we need to know the meaning of systolic blood pressure and diastolic blood pressure.

Systolic blood pressure is the level of blood pressure in the arteries when the heart contracts. On the other hand, diastolic blood pressure is the level of blood pressure in the arteries between contraction of the heart (between heart beats). The unit of blood pressure is mmHg which stands for "millimeters of mercury" as the traditional equipment to measure blood pressure uses mercury in the tube and blood pressure is measured against the pressure produced by the height of mercury in the tube. 

Normal blood pressure : Systolic blood pressure is less than 120 mmHg and diastolic blood pressure is less then 90 mmHg. It is reported as < 120/80 mmHg.

Prehypertension : Systolic blood pressure is 120-139 mmHg and diastolic blood pressure is 80-99 mmHg. It is reported as 120-139/80-89 mmHg. Although people with this level of blood pressure don't have hypertension yet, they are at risk of developing hypertension later on. 

Hypertension :

Stage 1: Blood pressure 140-159/90-99 mmHg.

Stage 2: Blood pressure 160 or greater/100 or greater mmHg.

Note that if systolic blood pressure and diastolic blood pressure do not fall in the same category as mentioned above, the person is said to have the level of blood pressure in the category of higher level of blood pressure. For example, if your blood pressure is 145/110 mmHg, you are considered as having stage 2 hypertension.

The reason we have to stage hypertension is because it gives physicians and patients the information on the severity and plan for work-ups and management differently for each stage of hypertension.