ACLS guide to answering your cholesterol questions

ACLS guide to answering your cholesterol questions

Ahmed Raza

What is cholesterol?

Cholesterol in the body is a waxy, fat-like substance found in cell walls that come from two sources: the body and the food we eat. The body, especially the liver, makes all the cholesterol it needs, and this is used to make essential substances like hormones and bile acids. Bile acids facilitate digestion and absorption of lipids in the small intestine.

Cholesterol circulates in the blood throughout the body and is transmitted through the blood plasma. The body uses it to form cell membranes and hormones; it is a fundamental part of the structural component of human cell membranes.

Why is cholesterol important?

Cholesterol is essential for the body because it produces bile acid, vitamin D, and steroid hormones. However, excessive cholesterol in the blood may be harmful.

Cholesterol is recycled by way of being first excreted by the liver through the bile, from which it then goes into the digestive tract. Almost half of all excreted cholesterol is reabsorbed into the bloodstream courtesy of the small bowel.

Understanding cholesterol levels

The National Institutes of Health (NIH) recommends everyone over the age of 20 have their cholesterol checked once every five years. A majority of cardiologists recommend a fast of 12 hours before a cholesterol test because triglycerides can shoot up 20%–30% after a meal. Alcohol will also cause a triglyceride surge.

The blood test, lipoprotein profile, or lipid panel, provides the following:

Very low-density lipoprotein, or VLDL, makes up 10%–15% of total cholesterol. It is a known kind of lipoprotein manufactured by the liver and is a precursor of LDL. The purpose of VLDL is to move cholesterol and other lipids through the bloodstream. VLDL is regarded as the human body’s internal transmission system for lipids.

The LDL is calculated by plugging the measurements for total cholesterol, HDL, and triglycerides into an equation: Total cholesterol — HDL — (Triglycerides ÷ 5) = LDL.

LDL can also be measured directly in a non-fasting blood sample, as when triglycerides exceed 300 mg/dL (3.36 mmol/L)—when triglycerides are this high, the calculation will not be accurate.

A cholesterol ratio is often used to assess a person’s risk for heart disease. The HDL number is divided into the total cholesterol number. An optimal ratio is reported as less than 3.5-to-1. A higher ratio means a higher risk of heart disease.

Cholesterol categories

Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. A full lipoprotein profile needs to be completed if the total cholesterol is greater than 200 mg/dL or if the HDL is less than 40 mg/dL. Table 1 shows the total cholesterol level in relation to its category and Table 2 displays LDL level in relation to its category.

Table 1

Total cholesterol level and category

Total cholesterol level Category
Less than 200 mg/dL Desirable
200–239 mg/dL Borderline high
240 mg/dL and above High

Note. Retrieved from the NIH.

Table 2

LDL cholesterol level and category

LDL cholesterol level LDL-cholesterol category
Less than 100 mg/dL Optimal
100–129 mg/dL Near optimal/above optimal
130–159 mg/dL Borderline high
160–189 mg/dL High
190 mg/dL and above Very high

Note. Retrieved from the NIH.

If outside of the U.S. take the U.S. mg/dL limits for all the numbers and divided by 38.66, which is the conversion factor. A U.S. cholesterol number of 200 mg/dL is the same as a SI (International System of Units) cholesterol number of 200/38.66 = 5.17 mmol/L.

What affects cholesterol levels?

Many factors can affect cholesterol levels.

Cholesterol levels and heart disease

High blood cholesterol, or hyperlipidemia, is prevalent in America and is one of the major risk factors for developing heart disease; therefore, it is crucial to monitor cholesterol levels along with assessing other risk factors.

Heart disease and damaged arteries are associated with high cholesterol, but having high cholesterol doesn’t necessarily mean a person will develop heart disease. Risk factors for heart disease include:

The NIH explains that the more risk factors a person has, the greater the chances are of developing heart disease or having a heart attack. Some people are at high risk because they already have heart disease and other people are at high risk for developing heart disease because of a combination of risk factors.

Low cholesterol, or hypolipidemia, is better than high cholesterol most of the time, such as when taking cholesterol-lowering agents, such as statins, to lower high cholesterol.

It is when the cholesterol level drops for no apparent reason that is of concern. Further research is needed in the area of low cholesterol because cholesterol is vital for the production of hormones and brain function.


While high cholesterol can be a daunting issue for a person, there are many healthy benefits in trying to stave off out-of-control cholesterol levels. Having the right mix of attitude and determination can do a great deal to ensure that cholesterol levels do not get too high.

For example, one can engage in a certain amount of cardiovascular exercise a few times a week, such as walking or running for up to 30 minutes, which really makes a difference in keeping high levels of bad cholesterol at bay. Additional good advice is to eat a balanced diet with lean meat, vegetables, whole-grains, and fruits and avoid processed foods and sugar.


What is cholesterol:

Questions and answers on cholesterol and health with NHLBI nutritionist Janet de Jesus, M.S., R.D.:

Bile acids and metabolic regulations:

Millan J. et al. . Lipoprotein ratios: Physiological significance and clinical usefulness in cardiovascular prevention. Vascular health and risk management 5, 757–765 (2009). Retrieved from:

High cholesterol facts:

VDLD test:

Information on the development of the 2020-2025 Dietary Guidelines for Americans:

What is metabolic syndrome:

High blood cholesterol: What you need to know:

Medline plus cholesterol information:

Written by on Apr 4, 2017

Sarah has worked in various roles at Coffee Medical Center including nurse, education director, and quality assurance director.

Last reviewed and updated by on Feb 17, 2020

Dr. Michael A. Tomeo is the former chief of dermatology at Holy Redeemer Hospital. He maintains a teaching appointment at Hahnemann University as a clinical instructor of dermatology.

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