What Is LDL Cholesterol? - Definition & Normal Levels

Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

You've probably heard of 'bad' cholesterol. What is it and what does it mean for your health? Find out in this lesson, then check your understanding with the quiz at the end.


Cholesterol is a type of fat that our bodies produce. Your liver makes all the cholesterol you need. Cholesterol is also found in foods of animal origin, such as meat, poultry, and dairy products, and if you eat a diet high in saturated fats, the liver will make even more cholesterol. The two types of cholesterol that carry fat around the body are LDL and HDL.

Cholesterol: Bad vs. Good

LDL stands for low-density lipoprotein. Like all fats, cholesterol can't dissolve in blood, which is mostly water, so it attaches itself to a protein. 'Lipo' means fat, thus 'lipoprotein'. The protein acts like a bus, traveling around the body via the bloodstream and taking the LDL cholesterol where it needs to go.

LDL cholesterol transports its fat molecules onto the walls of arteries, causing plaque to form. This is known as atherosclerosis, or hardening of the arteries. Atherosclerosis narrows the artery, making it difficult for the blood to flow through freely, which can lead to blood clots and even blockages in the artery.

This is why LDL cholesterol is known as the 'bad' cholesterol. But there is also a 'good' cholesterol. Unlike its artery-hardening counterpart, HDL cholesterol travels around the body, picking up extra fat and returning it to the liver to be disposed of, rather like a garbage truck.

Testing for Bad Cholesterol Levels

There are no symptoms for high levels of LDL cholesterol, so it is recommended to have a baseline test done at age 20 and then follow-ups every five years. Finding any problems early means they are easier to treat and before major issues arise, such as a heart attack or stroke.

The test is a simple blood test and includes your levels of total cholesterol, HDL cholesterol, and triglyercides. It is a basic test that is usually offered as part of routine health screening.

All of us have some degree of plaque deposits in our arteries since it starts in childhood. However, the location (such as in the torso or limbs) and degree of plaque buildup can indicate your risk of heart attack or stroke.

Factors that increase LDL cholesterol levels include:

• Smoking

• Being overweight

• Sedentary lifestyle

• Not eating enough fiber

Changing these factors can lower LDL levels without having to take medications.

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