Low-density lipoprotein (LDL) cholesterol is a type of cholesterol in the blood. Blood tests can help determine a person’s LDL cholesterol levels. Having unhealthy levels of LDL cholesterol may increase a person’s risk of serious conditions, such as heart disease.

Cholesterol moves around a person’s body via lipoproteins in their bloodstream. There are two types in the blood: LDL cholesterol and high-density lipoprotein (HDL) cholesterol. Some people may refer to LDL as “bad” cholesterol and HDL as “good” cholesterol.

The body uses cholesterol to make cells, vitamins, and various hormones. However, high levels of cholesterol can increase a person’s risk of heart disease.

LDL blood tests can help a doctor monitor a person’s LDL cholesterol levels and treat any issues quickly.

This article will cover what an LDL test is, why it can be necessary, and how medical professionals and people at home carry out the test.

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LDL tests are a form of blood test that doctors use to measure the amount of LDL cholesterol in a person’s bloodstream. LDL tests can be part of a lipid panel test, or they can measure LDL levels directly.

Lipid panels can help doctors calculate LDL cholesterol levels by measuring the following:

  • total cholesterol
  • HDL cholesterol levels
  • triglycerides, which are the most common type of fat in the blood

The number of LDL cholesterol particles that a person has can help a doctor determine their risk of cardiovascular disease. High numbers of LDL cholesterol particles can mean that a person has a higher chance of developing blocked arteries.

Learn more about LDL cholesterol here.

A doctor can use the measurements of the three components above to estimate a person’s LDL cholesterol levels. A lipid panel generally provides fairly accurate results. However, certain factors, such as high triglyceride levels, can impair the accuracy of this test.

If a lipid panel cannot provide accurate information, a doctor may use a direct LDL cholesterol test. A direct LDL cholesterol test measures the actual amount of LDL cholesterol in a person’s blood.

Some people with healthy LDL cholesterol levels can still be at risk of cardiovascular disease. For these individuals, a doctor may also use an LDL particle test (LDL-P). LDL-P tests can measure the number, size, and density of the LDL cholesterol particles in the blood.

At-home cholesterol tests vs. clinical testing

A person can test their cholesterol levels at home, or doctors can carry out the test for them.

Using home testing kits can give a person an idea of their total cholesterol levels. A person’s total cholesterol is the sum of all their cholesterol levels. However, home testing kits do not provide the levels of specific types of cholesterol, such as LDL cholesterol.

Medical professionals carry out clinical LDL cholesterol tests in a controlled environment to ensure accurate results. However, if a person follows the instructions correctly, a home testing kit can be almost as accurate as a clinical test. Additionally, home testing kits can provide results within minutes instead of days.

A person may find that home testing kits are a convenient way to monitor their cholesterol levels. However, home testing kits cannot take the place of a professional screening and diagnosis.

Learn more about cholesterol tests here.

The Centers for Disease Control and Prevention (CDC) note that a person with high cholesterol levels will generally have no symptoms. However, high levels of LDL cholesterol can cause a buildup of plaque in a person’s blood vessels.

Plaque is a substance comprising fat, cholesterol, calcium, and waste from body cells. Plaque can build up inside a person’s arteries, causing them to narrow or become blocked. A buildup of plaque can lead to:

It is, therefore, important that a person has their cholesterol levels checked regularly.

A doctor can also use LDL blood tests to monitor how well a person is responding to LDL-lowering treatment.

The American Heart Association (AHA) recommends that people over 20 years old with no risk factors for heart disease get their cholesterol levels checked every 4⁠–6 years. The CDC suggests that children aged 9⁠–11 years and adolescents aged 17⁠–21 years should also have a cholesterol level test.

A person may need to have cholesterol tests more often if they have certain risk factors, including:

  • heart disease
  • diabetes
  • family history of high cholesterol
  • smoking cigarettes
  • obesity
  • an unhealthy diet
  • high blood pressure
  • being aged 45 years and over for males or 55 years and over for females

Before having an LDL blood test, a person may have to fast for 9–12 hours. Fasting means that a person cannot eat or drink anything but water during this time. However, a doctor may decide that a person does not need to fast before their LDL blood test.

A study from 2017 suggests that differences between fasting and nonfasting LDL cholesterol levels are insignificant.

Research from 2018, however, suggests that people at higher risk may benefit from fasting before an LDL blood test. Due to this, it is important that people follow the instructions that their doctors give them.

A person should let their doctor know before an LDL blood test if they are unwell, pregnant, or taking certain medications. These factors can affect a person’s LDL cholesterol levels.

A person undergoing a direct LDL cholesterol test does not need to do anything to prepare for their test.

Learn more about fasting before a cholesterol test here.

During an LDL cholesterol blood test, a doctor will take a sample of the person’s blood from either their vein or a finger prick. They will then send the person’s blood sample to a laboratory for testing.

If a person is measuring their cholesterol using a home testing kit, they will prick their own finger to obtain a blood sample. They can then test the sample using an electronic device or paper that changes color depending on the person’s cholesterol level.

Once a doctor has a person’s LDL blood test results, they can talk with them about any necessary treatment.

The results of a cholesterol test will appear in milligrams per deciliter of blood (mg/dl). According to the CDC, the optimal level for LDL cholesterol is less than 100 mg/dl. The following table shows the classifications of other ranges of LDL cholesterol for adults aged 40–75 years:

Near/above optimalBorderline highHighVery high
100–129 mg/dl130–159 mg/dl160–189 mg/dl190 mg/dl and above

If a person has high LDL cholesterol levels, their doctor may ask them about their family history, health, and lifestyle to determine what treatment will suit them best.

Learn more about ideal cholesterol levels according to age here.

Doctors may advise a person with high LDL cholesterol to make the following changes where applicable:

  • stopping smoking
  • eating a diet low in saturated and trans fats
  • getting regular exercise
  • reaching or maintaining a moderate body weight
  • managing stress
  • getting enough sleep
  • limiting alcohol intake

A doctor may also prescribe certain medications to help lower a person’s LDL cholesterol levels.

Low levels of LDL cholesterol can be a positive result. However, they can sometimes be due to health issues, such as:

For this reason, it is advisable to discuss the results with a doctor.

Learn more about ways to lower cholesterol here.

LDL blood tests measure a person’s LDL cholesterol levels in their blood. Cholesterol plays an important role in a range of bodily functions. However, high levels of LDL cholesterol can put a person at risk of heart disease.

A person should have an LDL cholesterol level test every 4–6 years. People with certain risk factors should undergo more frequent testing.

Before having an LDL blood test, a person may need to fast for 9–12 hours. During the LDL blood test, a doctor will take a blood sample, which they will then send to a laboratory for testing. Once a doctor receives a person’s LDL blood test results, they can discuss any treatments the person may require.

Anyone who feels concerned about their cholesterol levels should speak with a doctor.