What is cholesterol?

Cholesterol is a type of lipid. It’s a waxy, fat-like substance that your liver produces naturally. It’s vital for the formation of cell membranes, certain hormones, and vitamin D.

Cholesterol doesn’t dissolve in water, so it can’t travel through your blood on its own. To help transport cholesterol, your liver produces lipoproteins.

Lipoproteins are particles made from fat and protein. They carry cholesterol and triglycerides (another type of lipid) through your bloodstream. The two major forms of lipoprotein are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

LDL cholesterol, or “bad cholesterol”

Low-density lipoprotein (LDL) is often called “bad cholesterol.” It carries cholesterol to your arteries. If your levels of LDL cholesterol are too high, it can build up on the walls of your arteries.

The buildup is also known as cholesterol plaque. This plaque can narrow your arteries, limit your blood flow, and raise your risk of blood clots. If a blood clot blocks an artery in your heart or brain, it can cause a heart attack or stroke.

HDL cholesterol, or “good cholesterol”

High-density lipoprotein (HDL) is sometimes called “good cholesterol.” It helps return LDL cholesterol to your liver to be removed from your body. This helps prevent cholesterol plaque from building up in your arteries.

When you have healthy levels of HDL cholesterol, it can help lower your risk of blood clots, heart disease, and stroke.

High cholesterol symptoms

In most cases, high cholesterol is a “silent” problem. It typically doesn’t cause any symptoms. Many people don’t even realize they have high cholesterol until they develop serious complications, such as a heart attack or stroke.

That’s why routine cholesterol screening is important. If you’re age 20 years or older, ask your doctor if you should have routine cholesterol screening. 

Risk factors

Factors that can increase your risk of bad cholesterol include:

• Poor diet. Eating saturated fat, found in animal products, and trans fats, found in some commercially baked cookies and crackers and microwave popcorn, can raise your cholesterol level. Foods that are high in cholesterol, such as red meat and full-fat dairy products, will also increase your cholesterol.
• Obesity. Having a body mass index (BMI) of 30 or greater puts you at risk of high cholesterol.
• Lack of exercise. Exercise helps boost your body’s HDL, or “good,” cholesterol while increasing the size of the particles that make up your LDL, or “bad,” cholesterol, which makes it less harmful.
• Smoking. Cigarette smoking damages the walls of your blood vessels, making them more prone to accumulate fatty deposits. Smoking might also lower your level of HDL, or “good,” cholesterol.
• Age. Because your body’s chemistry changes as you age, your risk of high cholesterol climbs. For instance, as you age, your liver becomes less able to remove LDL cholesterol.
• Diabetes. High blood sugar contributes to higher levels of a dangerous cholesterol called very-low-density lipoprotein (VLDL) and lower HDL cholesterol. High blood sugar also damages the lining of your arteries.