What Is Cholesterol?

The illustration shows a normal artery with normal blood flow (Figure A) and an artery containing plaque buildup (Figure B).


To understand high blood cholesterol (ko-LES-ter-ol), it is important to know more about cholesterol.
Cholesterol is a waxy, fat-like substance that is found in all cells of the body. Your body needs some cholesterol to work the right way. Your body makes all the cholesterol it needs.
Cholesterol is also found in some of the foods you eat.
Your body uses cholesterol to make hormones, vitamin D, and substances that help you digest foods.
Blood is watery, and cholesterol is fatty. Just like oil and water, the two do not mix. To travel in the bloodstream, cholesterol is carried in small packages called lipoproteins (lip-o-PRO-teens). The small packages are made of fat (lipid) on the inside and proteins on the outside. Two kinds of lipoproteins carry cholesterol throughout your body. It is important to have healthy levels of both:
Low-density lipoprotein (LDL) cholesterol is sometimes called bad cholesterol.
High LDL cholesterol leads to a buildup of cholesterol in arteries. The higher the LDL level in your blood, the greater chance you have of getting heart disease.
High-density lipoprotein (HDL) cholesterol is sometimes called good cholesterol.
HDL carries cholesterol from other parts of your body back to your liver. The liver removes the cholesterol from your body. The higher your HDL cholesterol level, the lower your chance of getting heart disease.
What Is High Blood Cholesterol?
Too much cholesterol in the blood, or high blood cholesterol, can be serious. People with high blood cholesterol have a greater chance of getting heart disease. High blood cholesterol on its own does not cause symptoms, so many people are unaware that their cholesterol level is too high.
Cholesterol can build up on the walls of your arteries (blood vessels that carry blood from the heart to other parts of the body). This buildup of cholesterol is called plaque (plak). Over time, plaque can cause narrowing of the arteries. This is called atherosclerosis (ath-er-o-skler-O-sis), or hardening of the arteries.
Special arteries, called coronary arteries, bring blood to the heart. Narrowing of your coronary arteries due to plaque can stop or slow down the flow of blood to your heart. When the arteries narrow, the amount of oxygen-rich blood is decreased. This is called coronary artery disease (CAD). Large plaque areas can lead to chest pain called angina (an-JI-nuh or AN-juh-nuh). Angina happens when the heart does not receive enough oxygen-rich blood. Angina is a common symptom of CAD.
Some plaques have a thin covering and burst (rupture), releasing fat and cholesterol into the bloodstream. The release of fat and cholesterol may cause your blood to clot. A clot can block the flow of blood. This blockage can cause angina or a heart attack.
Lowering your cholesterol level decreases your chance for having a plaque burst and cause a heart attack. Lowering cholesterol may also slow down, reduce, or even stop plaque from building up.
Plaque and resulting health problems can also occur in arteries elsewhere in the body.

High Blood Pressure

High blood pressure (HBP) is a serious condition that can lead to coronary heart disease, heart failure, stroke, kidney failure, and other health problems."Blood pressure" is the force of blood pushing against the walls of the arteries as the heart pumps out blood. If this pressure rises and stays high over time, it can damage the body in many ways.OverviewAbout 1 in 3 adults in the United States has HBP. HBP itself usually has no symptoms. You can have it for years without knowing it. During this time, though, it can damage the heart, blood vessels, kidneys, and other parts of your body.This is why knowing your blood pressure numbers is important, even when you're feeling fine. If your blood pressure is normal, you can work with your health care team to keep it that way. If your blood pressure is too high, you need treatment to prevent damage to your body's organs.Blood Pressure NumbersBlood pressure numbers include systolic (sis-TOL-ik) and diastolic (di-a-STOL-ik) pressures. Systolic blood pressure is the pressure when the heart beats while pumping blood. Diastolic blood pressure is the pressure when the heart is at rest between beats.You will most often see blood pressure numbers written with the systolic number above or before the diastolic, such as 120/80 mmHg. (The mmHg is millimeters of mercury-the units used to measure blood pressure.)The table below shows normal numbers for adults. It also shows which numbers put you at greater risk for health problems. Blood pressure tends to goes up and down, even in people who have normal blood pressure. If your numbers stay above normal most of the time, you're at risk.Categories for Blood Pressure Levels in Adults (in mmHg, or millimeters of mercury)Category Systolic(top number) Diastolic(bottom number)Normal Less than 120 And Less than 80Prehypertension 120-139 Or 80-89High blood pressureStage 1 140-159 Or 90-99Stage 2 160 or higher Or 100 or higherThe ranges in the table apply to most adults (aged 18 and older) who don't have short-term serious illnesses.All levels above 120/80 mmHg raise your risk, and the risk grows as blood pressure levels rise. "Prehypertension" means you're likely to end up with HBP, unless you take steps to prevent it.If you're being treated for HBP and have repeat readings in the normal range, your blood pressure is under control. However, you still have the condition. You should see your doctor and stay on treatment to keep you blood pressure under control.Your systolic and diastolic numbers may not be in the same blood pressure category. In this case, the more severe category is the one you're in. For example, if your systolic number is 160 and your diastolic number is 80, you have stage 2 HBP. If your systolic number is 120 and your diastolic number is 95, you have stage 1 HBP.If you have diabetes or chronic kidney disease, HBP is defined as 130/80 mmHg or higher. HBP numbers also differ for children and teens. (For more information, see "How Is High Blood Pressure Diagnosed?")OutlookBlood pressure tends to rise with age. Following a healthy lifestyle helps some people delay or prevent this rise in blood pressure.People who have HBP can take steps to control it and reduce their risks for related health problems. Key steps include following a healthy lifestyle, having ongoing medical care, and following the treatment plan that your doctor prescribes.