Lipoproteins

What are lipoproteins?

Lipoproteins are round particles made of fat (lipids) and proteins that travel in your bloodstream to cells throughout your body. Cholesterol and triglycerides are two types of lipids found in lipoproteins.

Your body makes different types of lipoproteins. High levels of certain lipoproteins can be harmful to your heart. But some lipoproteins have heart-protective benefits.

What are cholesterol and triglycerides?

Cholesterol and triglycerides are waxy fats that circulate in your blood. Your body produces and uses these fats differently:

• Cholesterol: Your liver makes cholesterol. You also get it from the food you eat, such as animal fats like meat and dairy products. This fat helps your body produce vitamin D and the hormones estrogen, testosterone and cortisol. It also helps build cells in your nervous system.
• Triglycerides: Your liver and intestines in your digestive system make triglycerides. When you eat a lot of fat and calories, your body produces even more triglycerides. It stores the excess in fat cells. These fat stores release triglycerides into your bloodstream when your body needs energy.

What are the types of lipoproteins?

There are five main types of lipoproteins:

• High-density lipoprotein (HDL) is the “good cholesterol.” It carries cholesterol back to your liver to be flushed out of your body. High levels of HDL reduce your risk of cardiovascular (heart) disease.
• Low-density lipoprotein (LDL) is the “bad cholesterol.” It increases your risk of coronary artery disease, heart attacks and stroke. LDL carries cholesterol that accumulates as plaque inside blood vessels. Plaque buildup can make blood vessels too narrow for blood to flow freely. This condition is atherosclerosis.
• Very low-density lipoproteins (VLDL) are another type of “bad cholesterol.” VLDLs carry triglycerides — and to a lesser degree, cholesterol — to your tissues.
• Intermediate-density lipoproteins (IDL) are created when VLDLs give up their fatty acids. They’re then either removed by your liver or converted into LDL.
• Chylomicrons are very large particles that also transport triglycerides.

What is lipoprotein (a) or LP(a)?

Lipoprotein (a) or LP(a) is a type of LDL (“bad cholesterol”). A second protein called apolipoprotein or apo(a) loops around it in segments called kringles. Apolipoprotein makes the LDL particles stickier. As a result, LP(a) builds up in blood vessels, increasing the risk of cardiovascular problems. High levels of LP(a) are a risk factor for atherosclerosis.

While diet and certain lifestyle choices can affect HDL and LDL levels, your genes determine your LP(a) levels. Some people inherit gene changes (mutations) that make them more prone to high LP(a) levels. These people have a higher risk of heart disease at a young age.

What is a lipid panel blood test?

Healthcare providers order lipid blood tests to measure total cholesterol in your blood. The tests provide individual results for HDLs, LDLs and triglycerides and total cholesterol.

Any cholesterol test is a simple blood draw that takes fewer than five minutes. You may get the test at your healthcare provider’s office, blood testing lab or hospital. For the most accurate results, you need to fast for eight to 12 hours before getting this blood test. You may also need to stop taking certain medicines before the test. You should follow your healthcare provider’s directions.

How is lipoprotein (a) tested?

It isn’t standard practice to test LP(a) levels. You’ll only have testing for LP(a) levels during a lipid blood test if your healthcare provider specifically requests it.

Providers typically order the test only for those who have known heart disease risk factors like:

• Personal history of heart problems.
• Family history of heart disease, especially heart events at a younger age in more than one first-degree relative.
• Unusually high LDL levels.
• Risk factors for familial hypercholesterolemia, an inherited condition that causes high LDL levels.

What’s the purpose of a lipid blood test?

High cholesterol rarely causes symptoms. Testing is the best way to identify cholesterol issues that affect your heart and blood vessels.

Healthcare providers use lipid blood tests for:

• Screenings: The blood test may be part of a routine physical exam. The test can identify if you’re at high risk for cardiovascular disease. Knowing you’re at risk can help you take steps to prevent heart attacks, strokes and other concerns.
• Diagnosis: You may get a cholesterol blood test to diagnose conditions like atherosclerosis.
• Monitoring: Test results can show if your cholesterol numbers are worsening and need treatment. They can also show if your results are improving in response to treatments.

How often should you get lipoprotein tests?

High lipoprotein and total cholesterol levels become more of a problem with age. As the risk rises, your healthcare provider may order more frequent tests.

Recommendations for lipid blood tests include:

• Screening for men and people assigned male at birth (AMAB) over 35 and women and people assigned female at birth (AFAB) over 45 years of age.
• Screening for men aged 20 to 35 and women aged 20 to 45 if they have increased risk for atherosclerosis.
• Screening in children once between ages 9 and 11 and then again between 17 and 21.

What is the normal range for lipoproteins?

Labs measure cholesterol and lipoproteins in milligrams per deciliter (mg/dL). Individual laboratories can use different techniques. That means results from the same blood sample can vary from lab to lab. When possible, your provider will want to use the same lab to monitor your levels.

Healthy ranges for HDLs, LDLs, triglycerides and total cholesterol vary by age and sex. Talk with your healthcare provider about what levels are healthy for you. In general, these numbers are in the healthy range if you have no other risk factors:

• Total cholesterol: 100-199 mg/dL for adults over 21 years old; 75-169 mg/dL for those aged 20 and younger.
• HDL (good cholesterol): 45 mg/dL or higher.
• LDL (bad cholesterol): Less than 100 mg/dL.
• Triglycerides: Less than 150 mg/dL.

A lipid blood test can’t measure VLDL levels, and there isn’t a separate test. Instead, labs estimate VLDL levels by dividing your triglyceride numbers by five. A healthy VLDL level would be less than 30 mg/dL. But this equation isn’t always accurate when triglyceride levels are too high.

What is the normal range for lipoprotein (a)?

Labs report LP(a) levels in mg/dL or nanomoles per liter (nmol/L). A reading above 50 mg/dL or 75 nmol/L is high and increases your risk for atherosclerosis, heart attacks and strokes.

What are the risk factors for high LDL (bad cholesterol)?

People who have gone through menopause and adults over 40 are most at risk for high LDL levels. But even children can have cholesterol problems. As you get older, your metabolism slows and your liver doesn’t remove bad cholesterol from your body as well.

Race and ethnicity also play a role. Asian Americans are more prone to high LDL levels, while white people are more likely to have high total cholesterol.

Additional risk factors for high LDL levels include:

• Diet high in calories, saturated fats and cholesterol.
• Conditions like diabetes and kidney disease.
• Family history of high cholesterol.
• Excessive alcohol use and smoking.
• Medications like corticosteroids and drugs that treat high blood pressure and HIV and AIDS.
• Carrying extra weight (obesity).

How is high LDL treated?

People at high risk for heart attacks, stroke and other issues due to high LDL levels often need cholesterol-lowering drugs like statins, ezetimibe, and PCSK9 inhibitors. You can also make dietary and lifestyle changes to improve your numbers.

What steps can you take to improve lipoprotein numbers?

Dietary and lifestyle changes can lower bad cholesterol (LDLs) and boost good cholesterol (HDLs). These steps can help:

• Be physically active for at least 150 minutes every week (that’s 30 minutes a day).
• Eat a heart-healthy diet that’s low in unhealthy fats and simple sugars (carbohydrates) and higher in fiber.
• Manage high blood pressure and diabetes.
• Get more sleep.
• Maintain a healthy weight. If you’re overweight, losing 5% to 10% of your body weight can improve cholesterol numbers.
• Find healthy ways to manage stress.
• Reduce your alcohol consumption.
• Seek help to quit smoking (nicotine raises LDL levels and lowers HDL levels).

A note from Cleveland Clinic

There are different types of lipoproteins. HDL is a “good cholesterol” that helps your body get rid of LDL, the “bad cholesterol” that clogs arteries. Your behaviors, including diet, smoking and exercise, affect lipoprotein levels. Some people inherit a gene change that causes high levels of lipoprotein (a) or LP(a). This “sticky” lipoprotein builds up in arteries, increasing your risk of heart disease. Lifestyle changes and medications like statins can lower LDL and LP(a) levels while boosting HDL.