Blood pressure measures the force that blood places against the artery walls as it's pumped through the body. It's an indicator of how hard the heart is working to supply the body with blood and oxygen it needs. Blood pressure is recorded as a fraction, such as 120/80mmHg. The top number is the systolic and represents the heart beating. The bottom is the diastolic, representing the heart at rest. When blood pressure gets too high, health problems can result. To help prevent serious illness, be aware of the complications that can occur when the bottom number is 100 or higher.
When blood pressure numbers reach between 120/80mmHg to 139/89mmHg, it's considered prehypertension. A level of 140/90mmHg or higher is considered high blood pressure or hypertension. A bottom reading of 100 or higher means the heart is working harder than it should. This may be due to coronary artery disease or another underlying condition. When the heart has to work that hard, the risk for a heart attack increases.
Because high blood pressure can exist without causing any symptoms, it's important to have it tested regularly so it can be caught in the early stages when it's easier to treat. Diastolic blood pressure or the bottom number is of more concern in younger people, because diastolic tends to naturally decrease with age and systolic tends to get higher with age, says the National Heart, Lung and Blood Institute.
When the top number reaches 180 or higher or the bottom number reaches 110 or higher, it's considered a hypertensive crisis, warns the American Heart Association. This is a medical emergency that requires immediate treatment. A hypertensive crisis may or may not cause nosebleeds, headaches, anxiety and trouble breathing. If left untreated, a hypertensive crisis can lead to fainting, seizures, swelling in the brain, memory loss, organ damage and many other health problems.
Having high diastolic blood pressure can raise the risk of a stroke. High blood pressure may be a signal that the arteries that supply the brain are blocked, meaning there is less blood and oxygen reaching the brain. In addition, untreated high blood pressure can cause bleeding within the brain--called a subarachnoid hemorrhage--which can also cause stroke, aneurysm and even dementia, the Mayo Clinic says. High diastolic blood pressure is even more of a concern if other chronic conditions exist such as diabetes, kidney disease, heart disease, or in patients who smoke or are overweight.
According to Merck, high diastolic or systolic blood pressure that goes untreated can also cause bleeding and swelling of the retina. The retina is the portion of the eye that sends signals to the brain so vision can be interpreted. When the retina swells, vision may be distorted or blurry. Blindness can occur in severe cases.