The normal blood pressure range is between 90-139 mmHg for high pressure and between 60-89 mmHg for low pressure. Hypertensive disorders are diagnosed if the high pressure is greater than or equal to 140 mmHg, and/or the low pressure is greater than or equal to 90 mmHg. A high pressure between 140-159 mmHg, and/or a low pressure between 90-99 mmHg, we define as hypertensive disease grade 1. A high pressure between 160-179 mmHg, and/or a low pressure between 100-109 mmHg, we define as hypertensive disease grade 2. If the high pressure is greater than or equal to 180 mmHg, and/or the low pressure is greater than or equal to 110 mmHg, we define as hypertension grade 3.