I was going through the portals in health to know more about the causes of high Blood pressure. I was surprised to know that the cause of high Blood pressure in 80 to 35 percent of people is without known cause. It is called essential hypertension. The other causes are also many in number and there are many disease in human that can increase blood pressure. Interestingly that is why doctors always check blood pressure even though you see him for stomach pain or headache or eye check up. If your doctor is not measuring, please ask him to measure to.