What are normal cholesterol levels?
Blood tests are required to measure total cholesterol and lipoproteins. For a complete lipoprotein analysis, the patient should be fasting for at least 12 hours.
The goal is to have patients modify lifestyle and diet to maintain cholesterol levels within the normal range. It is important to remember that HDL may protect a patient from heart disease and it may be a treatment goal to raise a too low level of HDL.
Quick GuideLower Your Cholesterol, Save Your Heart
Cholesterol definition and cholesterol lowering facts
- A high blood cholesterol levels is also referred to as hypercholesterolemia,
and is found in the blood circulation of humans.
- Cholesterol is a fatty substance that is an important part of the outer lining of cells in the body of animals. Because cholesterol is a fat (medically referred to as lipid), elevated blood cholesterol is sometimes referred to as hyperlipidemia.
- Cholesterol in the blood originates from dietary intake and
- Dietary cholesterol comes primarily from animal sources including meat, poultry, fish, and dairy products. Organ meats such as liver are especially high in cholesterol.
- LDL (low density lipoprotein) cholesterol is called "bad" cholesterol
because elevated levels of LDL cholesterol are associated with an increased risk of stroke, peripheral artery disease, or coronary heart disease (atherosclerotic cardiovascular disease, ASCVD).
HDL (high density lipoprotein) cholesterol is called the "good" cholesterol because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from artery walls and disposing of them through liver metabolism.
- High levels of LDL cholesterol and low levels of HDL cholesterol are risk factors for narrowing of the arteries in the body (atherosclerosis).
- Research has shown that lowering LDL cholesterol reduces the risk of heart attacks, strokes, and peripheral artery disease.
- The National Institute of Health, the American Heart Association, and the American College of Cardiology publish guidelines to help physicians and patients with this risk reduction for heart attack, stroke, and peripheral artery disease.
- Factors that affect blood cholesterol levels include diet, body weight, exercise, age and gender, diabetes, heredity, and underlying medical conditions.
- Guidelines recommend that cholesterol screening occur every 5 years after age 20. Should elevated cholesterol levels be found, testing may need to occur more frequently.
People with cardiovascular disease, type 2 diabetes, LDL cholesterol levels greater 190 mg/dL, and those with a 10-year heart disease risk of greater than 7.5% would benefit from moderate- to high-intensity statin drug therapy.
- Cholesterol-lowering statin medications decrease the risk of heart disease.
What is cholesterol?
- Cholesterol is a chemical compound that is naturally produced by the body and is structurally a combination of fat (lipid) and steroid.
- Cholesterol is a building block for cell membranes and for hormones like
estrogen and testosterone.
- About 80% of the body's cholesterol is produced by the liver, while the rest comes from our
- The main sources of dietary cholesterol are meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol.
- After a meal, dietary cholesterol is absorbed from the intestine and stored in the liver.
- The liver is able to regulate cholesterol levels in the bloodstream and can secrete cholesterol if it is needed by the body.
What are "normal" cholesterol blood levels?
There are no established "normal" blood levels for total and LDL cholesterol. In most other blood tests in medicine, normal ranges can be set by taking measurements from large number of healthy subjects. The normal range of LDL cholesterol among "healthy" adults (adults with no known coronary heart disease) in the United States may be too high. The atherosclerosis process may be quietly progressing in many healthy children and adults with average LDL cholesterol blood levels, putting them at risk of developing coronary heart disease in the future.
HDL cholesterol vs. LDL cholesterol
What is LDL cholesterol or the "bad" cholesterol?
- LDL cholesterol (low density lipoprotein) is called "bad" cholesterol, because elevated levels of LDL cholesterol are associated with an increased risk of coronary heart disease, stroke, and peripheral artery disease.
- LDL lipoprotein deposits cholesterol along the inside of artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the lumen of the arteries, a process called atherosclerosis, which decreases blood flow through the narrowed plaque-filled vessel.
- Narrowing of blood vessels in the heart may lead to angina or heart attack.
- Narrowing of blood vessels in the brain this may cause a transient ischemic attack (TIA) or stroke.
- Narrowing of the arteries throughout the body (peripheral artery disease) can lead to signs and symptoms of pain, including in the intestine (mesenteric ischemia) and in the legs with walking (claudication).
What is HDL cholesterol or the "good" cholesterol?
- HDL cholesterol (high density lipoprotein) is called the "good cholesterol" because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of them through the liver.
- High levels of LDL cholesterol and low levels of HDL cholesterol (high LDL/HDL ratios) are risk factors for atherosclerosis
and heart attacks
- Low levels of LDL cholesterol and high levels of HDL cholesterol (low LDL/HDL ratios) are desirable and protect against heart disease and stroke.
- Very low and very high HDL cholesterol levels can run in families. Families with low HDL cholesterol levels have a higher incidence of heart attacks than the general population, while families with high HDL cholesterol levels tend to live longer with a lower frequency of heart attacks.
- Like LDL cholesterol, lifestyle factors, and other conditions influence HDL cholesterol levels. HDL cholesterol levels tend to be lower in persons who smoke cigarettes or have type 2
diabetes and in those who are
overweight or inactive.
- HDL cholesterol is higher in people who are lean, exercise regularly, and do not smoke cigarettes.
- Estrogen increases a person's HDL cholesterol, which explains why women generally have higher HDL levels than men.
- The combination of low levels of total and LDL cholesterol and high levels of HDL cholesterol is favorable.
What does "total" cholesterol mean?
- Total cholesterol is the sum of LDL (low density) cholesterol, HDL (high density) cholesterol, VLDL (very low-density) cholesterol, and IDL (intermediate density) cholesterol.
What determines the level of LDL or "bad" cholesterol in the blood?
- The liver manufactures and secretes LDL cholesterol into the blood. It also removes LDL cholesterol from the blood by active LDL receptors on the surface of its cells. A decrease in the number of liver cell LDL receptors is associated with high LDL cholesterol blood levels.
- Both heredity and
diet have a significant influence on a person's LDL, HDL, and total cholesterol levels. For example, familial hypercholesterolemia (an inherited form of very
high cholesterol in the blood) is an inherited disorder whose victims have a diminished number or nonexistent LDL receptors on the surface of liver cells. People with this disorder also tend to develop atherosclerosis and heart attacks during early adulthood.
- Diets that are high in saturated
fats and cholesterol raise the levels of LDL cholesterol in the blood. Fats are classified as saturated or unsaturated (according to their chemical structure). Saturated fats are derived primarily from meat and dairy products and can raise blood cholesterol levels. Some vegetable oils made from coconut, palm, and cocoa are also high in saturated fats.
Medically Reviewed by a Doctor on 12/1/2016