What is normal blood pressure? Normal blood pressure is essential for life. Without the pressure to force our blood to flow through the circulatory system, oxygen and nutrients would not reach our tissues and organs through our arteries. Blood pressure, however, can become dangerously high or too low. In this article, we will discuss what blood pressure is, how it is measured and what the measurements mean for our health. What is blood pressure? Blood pressure is the force that moves blood through the circulatory system. It is an important force because, without blood pressure, oxygen and nutrients in the circulatory system could not be pushed to nourish tissues and organs. Blood pressure is also important because it delivers white blood cells and antibodies for immunity and hormones such as insulin. Just as important as delivering oxygen and nutrients is the fact that the fresh blood we receive can pick up the toxic waste products of metabolism, including the carbon dioxide we exhale with every breath and the toxins we clean up through the liver and kidneys. Blood itself has a number of other properties, including its temperature. It also carries one of the proteins against tissue damage, namely clotting platelets, which prevent blood loss after injury. But what exactly causes blood pressure in the arteries? Part of the answer is simple - the heart creates blood pressure by pushing blood out with each heartbeat. However, it is not just the pumping of the heart that can create blood pressure. What is normal blood pressure? Normal blood pressure is defined for most adults as a systolic pressure below 120 and a diastolic pressure below 80. Elevated blood pressure is defined as a systolic pressure between 120 and 129 and a diastolic pressure below 80. Which number is most important for blood pressure? For many years, systolic blood pressure has been considered important. This is based on research, including the famous Framingham Heart Study, which shows that high systolic blood pressure is a stronger predictor of heart disease and stroke. What is the function of blood pressure in the body? The circulatory system is similar to a very complex system of pipes with blood 'flowing' and arteries 'piping'. The flow of blood is governed by a fundamental law of physics and this law also applies to a garden hose. Blood flows through the body because of pressure differences. Blood pressure is highest at the beginning of its journey from the heart as it enters the aorta and lowest at the end of its journey along successively smaller arterial branches. This difference in pressure causes blood to flow. Arteries affect blood pressure in a similar way to the physical properties of a garden hose pipe, which affects water pressure. Narrowing of the tube increases the pressure at the point of narrowing. Without the elastic nature of the artery walls, for example, blood pressure would fall faster as blood is pumped out of the heart. Although the heart creates maximum pressure, the properties of the arteries are equally important for maintaining it and allowing blood to flow throughout the body. The condition of the arteries affects blood pressure and blood flow, and narrowing of the arteries can eventually block the blood supply completely, leading to dangerous conditions including stroke and heart attack. When is the best time to measure blood pressure? Take it first thing in the morning, before eating or taking medication. Take it again in the evening. Each time you take a reading, take two or three readings so that the results are the same. Your healthcare provider may recommend that you take your blood pressure at the same time every day.