What is serum cholesterol?

Cholesterol is a type of body fat, or lipid. A serum cholesterol level is a measurement of certain elements in the blood, including the amount of high- and low-density lipoprotein cholesterol (HDL and LDL) in a person’s blood.

Serum cholesterol levels also show the amount of triglycerides present. Triglycerides are another lipid that can be measured in the blood.

According to the American Heart Association, low-density lipoprotein (LDL) cholesterol is often considered bad, while high-density lipoprotein (HDL) cholesterol is considered good.

A person’s serum cholesterol level can indicate their risk for conditions such as heart disease.

In this article, we explore what serum cholesterol shows, what healthy ranges are, and how to improve levels with changes to lifestyle and diet.

What is serum cholesterol?

Cholesterol is a waxy, fatty substance. Some cells in the liver produce it and release it into the bloodstream.

LDL cholesterol can build up in a person’s arteries, clogging them and reducing blood flow. This is why cholesterol is often linked to heart disease.

With a blood test, a doctor can measure levels of:

• HDL cholesterol, which is good
• LDL cholesterol, which is bad
• triglycerides, which are a type of fat bundled with cholesterol

Total serum cholesterol is calculated by adding the HDL level, the LDL level, and 20 percent of the triglyceride level present in a blood sample.

Cholesterol plays a vital in many of the body’s processes, including:

• building cellular membranes
• making hormones
• metabolizing vitamin D in the skin
• producing bile acids to digest fatty foods

While LDL cholesterol tends to build up and block arteries, HDL cholesterol helps to mop up other cholesterol in the blood and unstick it from artery walls. This is why HDL cholesterol is considered good.

Normal ranges

Doctors once determined whether a person’s serum cholesterol level was healthy by comparing it to established normal ranges.

Previously used guidelines, reported in milligrams per deciliter (mg/dL) of blood, include:

Age and sex	Total serum cholesterol	HDL level	LDL level	Triglycerides
All aged 19 and younger	At most 170 mg/dL	At least 45 mg/dL	Less than 100 mg/dL	Less than 150 mg/dL
Females aged 20 and older	125–200 mg/dL	At least 50 mg/dL	Less than 100 mg/dL	Less than 150 mg/dL
Males aged 20 and older	125–200 mg/dL	At least 40 mg/dL	Less than 100 mg/dL	Less than 150 mg/dL

Doctors now take a wider range of factors into account before deciding if someone’s cholesterol levels are unhealthy or require treatment.

Some risk factors a doctor may consider when evaluating a serum cholesterol level include:

• the ratio of HDL to LDL cholesterol
• triglyceride levels
• obesity
• high blood pressure
• whether the person is a male aged 45 years or older
• whether the person has experienced menopause
• smoking or tobacco use
• family history
• type 2 diabetes
• lack of physical activity or a sedentary lifestyle
• a diet high in saturated and trans fats
• excessive alcohol consumption
• a diet very high in carbohydrates, especially when refined
• metabolic syndromes
• chronic inflammatory conditions

Health impacts of serum cholesterol levels

Overall, a person with higher levels of HDL cholesterol and lower levels of LDL cholesterol will have a healthier serum cholesterol measurement.

This is because HDL cholesterol helps to reduce the presence of LDL cholesterol in the blood. It can also prevent LDL cholesterol from collecting and forming hard deposits called plaques, which stick to artery walls and reduce blood flow.

Plaques can become so large that they cause the arteries to narrow and stiffen, which can contribute to heart disease.

A significant amount of LDL cholesterol in arteries can prevent enough blood and oxygen from reaching organs and tissues, causing severe health complications.

A chunk of a plaque, known as a thrombus or blood clot, can also break off and become stuck in a narrower or restricted artery. This will make the blockage of blood more severe.

Complications associated with high serum cholesterol levels include:

• coronary artery disease
• stroke
• heart attack
• organ or tissue damage

Less is known about how triglycerides impact health. However, people with high levels of triglycerides tend to be at risk for similar conditions, including diabetes, high blood pressure, and heart disease.

Below is a 3-D model of high cholesterol, which is fully interactive.

Explore the model, using your mouse pad or touchscreen, to understand more about the impact of high cholesterol levels.

Source: Medical News Today