I. Introduction

According to the Centers for Disease Control and Prevention, heart disease is the most common cause of death among men and women in the United States, accounting for approximately 647,000 deaths each year. In addition to the toll it takes on human life, heart disease is a serious public health issue, as it is expensive to manage and contributes to a loss of economic productivity.

This guide provides an overview of the LDL cholesterol test, including how the test is performed and what the results mean. It also contains information on heart disease, such as what causes it and how it can be treated.

II. Overview of the LDL Cholesterol Test

Why should I get tested?

The purpose of the LDL cholesterol test is to determine if an individual has a high level of low-density lipoprotein in the blood. It’s important to get tested because early detection of high LDL levels provides an opportunity to make lifestyle changes or take medications that can reduce the risk of heart disease and heart attack. The test is also important for people who have certain risk factors for heart disease, such as obesity, Type 2 diabetes, or a history of smoking cigarettes.

When should I get tested?

Experts from the Centers for Disease Control and Prevention recommend that healthy adults have their cholesterol levels checked every four to six years. Adults with heart disease, a family history of high cholesterol, or diabetes need to have their cholesterol levels checked more often. Children should also have their cholesterol levels checked, but not as often as adults. The CDC recommends one cholesterol test between the ages of 9 and 11 and another test between the ages of 17 and 21.

What is required for the test?

The LDL test is a blood test, so the individual must provide a blood sample for analysis.

What do I need to do to prepare for the test?

Some health care providers want their patients to fast for nine to 12 hours before any cholesterol tests. Fasting means consuming no food or beverages other than water.

III. The Basics of Heart Disease

Heart disease is a general term used to describe several conditions that affect the heart. In the United States, the most common form of heart disease is coronary artery disease, which restricts blood flow to the heart and increases the risk of heart attack and other complications. Several risk factors make it more likely that an individual will develop heart disease. Three of the most significant risk factors are smoking, high levels of cholesterol, and high blood pressure. Diabetes, obesity, excessive alcohol intake, a lack of physical activity, and a diet high in saturated fat also increase the risk of heart disease.

Heart disease does not always cause symptoms right away. In fact, some people don’t know they have heart disease until they suffer a heart attack or develop heart failure. The symptoms of a heart attack include chest pain, pain that radiates down the left arm, pain in the jaw, upper back pain, neck pain, extreme fatigue, nausea, dizziness, vomiting, indigestion, and shortness of breath. Heart failure can cause shortness of breath, swelling of the feet and ankles, leg swelling, fatigue, or swelling in the neck. Some people with heart disease develop arrhythmias, which are abnormal heart rhythms. The main symptom of arrhythmia is heart palpitations or sensations of fluttering in the chest.

Heart disease is typically diagnosed based on the results of blood tests and imaging tests, along with information about an individual’s family medical history. An echocardiogram, a type of ultrasound that focuses on the heart and coronary arteries, can be used to determine if the heart is pumping normally. It also helps detect any narrowing of the coronary arteries, which can indicate that an individual has an elevated risk of heart attack. An electrocardiogram helps identify any abnormalities in an individual’s heart rhythm.

Stress testing helps determine how well the heart works when it’s under stress. During an exercise stress test, the individual exercises on a treadmill while hooked up to a machine that records data such as heart rate, blood pressure, and the electrical activity of the heart. For people who can’t exercise on a treadmill because they’re injured or in poor health, the nuclear stress test is another option. During a nuclear stress test, a radioactive substance is injected into one of the individual’s veins. This helps healthcare professionals determine if the heart gets enough blood flow when it’s under stress versus when it’s at rest.

IV. How an LDL Cholesterol Test Works

A person’s LDL level can be determined in two ways. Some labs perform a direct LDL measurement, while others calculate LDL by using the Friedewald formula. The formula is LDL = total cholesterol (TC) minus HDL cholesterol (HDL) minus triglycerides (TGs)/5. HDL cholesterol, also called high-density lipoprotein, is the “good” cholesterol found in the bloodstream, while triglycerides are a type of fat. Using this calculation, a person with a total cholesterol of 190, an HDL level of 50, and a triglyceride level of 100 would have an estimated LDL level of 120 (190 – 50 – 100/5). In labs that perform direct LDL measurement, laboratory personnel use specialized machines to distinguish LDL from other particles and determine how much of it is present in a blood sample.

To have the LDL test, an individual must provide a blood sample. In many cases, people have their blood drawn in a hospital, outpatient laboratory, or other medical facility, however, home test kits are now available for increased convenience. These kits typically come with a lancet that can be used to prick one of the fingers and collect a blood sample. Once the sample has been analyzed, the individual typically receives a written report with the results.

V. Treatment for Heart Disease

No single treatment plan is effective for every case of heart disease, so it’s important for people with high LDL levels to be monitored closely by their primary care physicians. It may also be necessary to see a cardiologist — a doctor who specializes in diagnosing and treating heart conditions — at least once per year.

Lifestyle Changes

Lifestyle changes are often the first line of defense for someone with a high LDL level, as factors such as smoking, living a sedentary lifestyle, and consuming foods high in saturated fats and cholesterol can increase the risk of heart disease, stroke, and other complications. The chemicals found in tobacco damage the blood vessels and impair the function of the heart, so it’s important to stop smoking cigarettes and chewing tobacco. The American Heart Association recommends following a diet that emphasizes fruits, vegetables, poultry, legumes, fish, and low-fat dairy products and limits red meats, sweets, and beverages sweetened with sugar. People with heart disease should also aim to exercise daily and lose any excess weight. Getting at least 150 minutes of exercise each week can help reduce LDL levels, and shedding extra weight can reduce the risk of high blood pressure and diabetes.

Medications

Several types of medications are used to treat heart disease and reduce the risk of complications. These medications include anticoagulants, beta-blockers, ACE inhibitors, vasodilators, diuretics, and cholesterol-lowering drugs. Anticoagulants, also known as blood thinners, make it more difficult for the blood to form clots. In people with heart disease, this can reduce the risk of stroke by preventing dangerous blood clots from forming. Beta-blockers slow an individual’s heart rate and help to lessen the force of each beat; this lowers blood pressure and reduces the workload of the heart.

ACE inhibitors, or angiotensin-converting enzyme inhibitors, lower blood pressure by decreasing levels of angiotensin II in the blood. Angiotensin II causes the blood vessels to constrict, forcing the heart to work harder to pump blood. Reducing the amount of angiotensin II in the blood allows the vessels to dilate, making it easier for the heart to pump blood to other parts of the body. Vasodilators relax the blood vessels and increase the amount of oxygen supplied to the heart, reducing the heart’s workload. Diuretics remove excess fluid from the body, easing the workload of the heart and relieving swelling in the feet, legs, and ankles. These medications also can lower blood pressure.

Cholesterol-lowering medications reduce the amount of LDL in the blood, which also decreases an individual’s total cholesterol level. Statins are the “gold standard” for reducing cholesterol, but cholesterol absorption inhibitors or nicotinic acids may be used in people for whom statins are ineffective or cause intolerable side effects.

Medical Procedures

If lifestyle changes and daily medications do not prevent heart disease from getting worse, an individual may have to have one or more medical procedures to treat blocked vessels. When a blood clot is blocking one or more of the coronary arteries, thrombolytic therapy can dissolve the blockage. Thrombolytic therapy involves administering medications through an intravenous line (IV). Dissolving the clot improves blood flow to the heart and other parts of the body.

Coronary angioplasty and stent implantation are used to open up blood vessels that have become too narrow due to the accumulation of plaque. During coronary angioplasty, a balloon catheter is introduced into the narrow vessel. Once the balloon reaches the site of the blockage, it is inflated, flattening plaque against the wall of the vessel and improving blood flow. To keep the vessel open, a doctor inserts a small tube called a stent where the blockage used to be. Some stents are simple pieces of metal, while others — known as drug-eluting stents — are coated with medications that reduce the risk of scarring and clots. Drug-eluting stents prevent the artery from becoming blocked again.

If these procedures do not work, or if an individual is a poor candidate for angioplasty and stenting, it may be necessary for a surgeon to perform coronary artery bypass graft surgery. Known as CABG (“cabbage”), this surgery involves removing a blood vessel from the chest or one of the limbs and attaching it to the blocked coronary artery. This allows blood to flow around the blockage, relieving chest pain and reducing the risk of a heart attack.

VI. FAQs

What is a normal LDL cholesterol level?

The LDL test is a little different from many other blood tests because the results are reported as optimal, near optimal, borderline high, high, and very high instead of just normal or abnormal. According to MedlinePlus, LDL levels of less than 100 milligrams per deciliter (mg/dL) are optimal. LDL levels of 100 to 129 mg/dL are near optimal, LDL levels of 130 to 159 mg/dL are borderline high, LDL levels of 160 to 189 mg/dL are high, and LDL levels of 190 mg/dL and above are very high.

Why did my doctor ask me to fast before having my LDL checked?

LDL is often calculated based on an individual’s total cholesterol, HDL, and triglyceride levels. In a study to determine how much of an effect fasting has on cholesterol results, researchers found that eating right before a blood test does not really affect total cholesterol, HDL cholesterol, or LDL cholesterol, but it does affect an individual’s triglyceride levels. Since LDL is often calculated based on total cholesterol, HDL cholesterol, and triglycerides, anything that results in an increased triglyceride level should be avoided; otherwise, the LDL calculation may not be as accurate as possible.

My doctor ordered a lipid panel. How is this different from the LDL test?

The LDL test only measures the amount of LDL cholesterol in the blood, while the lipid panel measures total cholesterol, triglycerides, HDL, LDL, and very low-density lipoprotein (VLDL), a type of cholesterol associated with arterial plaque. A lipid panel provides more information to help determine an individual’s risk of developing heart disease.

What's the difference between LDL and HDL cholesterol?

LDL is the bad cholesterol that contributes to plaque buildup and increases an individual’s risk of developing heart disease. In contrast, HDL appears to have a protective effect, as it helps remove LDL from the bloodstream. A low level of HDL is associated with an increased risk of heart disease, just like a high level of LDL is associated with an increased risk of heart disease.

If my LDL cholesterol is normal, does that mean I won't develop heart disease?

No. It’s possible to have an optimal or near-optimal LDL level and still develop heart disease. LDL is only one of the risk factors associated with heart disease, so anyone who smokes, doesn’t get enough exercise, eats a diet high in cholesterol and saturated fats, or has a history of diabetes or high blood pressure can still develop heart disease even with a normal LDL level. In fact, about 50% of all heart attacks occur in people who have normal cholesterol levels, according to experts from Harvard Medical School.

Is my LDL level always the same?

No. LDL fluctuates based on several factors, including what you eat and how much cholesterol your liver produces.

VII. Additional Resources

NameWebSummary
American Heart Associationwww.heart.orgThe American Heart Association provides detailed information on heart disease, including tips for making healthy lifestyle choices.
Johns Hopkins Medicinewww.hopkinsmedicine.orgLearn why it’s important to have your cholesterol checked regularly.
Centers for Disease Control and Preventionwww.cdc.govThe CDC offers detailed statistics on heart disease, including how many Americans have it and how many heart attacks occur each year in the United States.
MedlinePluswww.medlineplus.govLearn more about the different types of heart disease and how they affect the body.
National Heart, Lung, and Blood Institutewww.nhlbi.nih.govThe NHLBI provides detailed information on ischemic heart disease, a type of heart disease that occurs when narrowed arteries can’t deliver enough blood to the heart.

VIII. Sources Used in This Article