Cholesterol is one of the three main lipids in the body and is a major risk factor in the development of certain diseases like coronary heart disease. There are a number of important functions of cholesterol and it is manufactured in the liver (endogenous cholesterol) or to a lesser extent, it is sourced from food (exogenous cholesterol).
Cholesterol is transported in the blood stream by bonding to lipoproteins. High-density lipoprotein or HDL cholesterol is referred to as the “good cholesterol” because it carries cholesterol away from tissues, to the liver where it is broken down and passed out in the bile. Low-density lipoproteins or LDL cholesterol is considered as the “bad cholesterol” because it carries cholesterol to various tissues and circulates the cholesterol in the body.
Total Blood Cholesterol Test
It is common practice to conduct a total cholesterol test to assess a person who is at risk of hypercholesterolemia. A total blood cholesterol will indicate the levels of all the cholesterols in the blood and does not provide specific values for each type of lipid and lipoprotein. While the most accurate results will be acquired after a minimum of an 8 hour fast (ideally 9 to 12 hours), routine screening does not require fasting. This type of screening may be conducted for insurance purposes or to identify a person who is at risk and requires further testing.
Total Cholesterol Levels (Values and Reference Range)
- Optimal : less than 200 mg/dL (5.18 mmol/L)
- Borderline High = 200 to 239 mg/dL (5.18 to 6.18 mmol/L)
- High : greater than 240 mg/dL (6.22 mmol/L)
Lipid Profile Test
A lipid profile should be conducted for a person with known risk factors associated with both cardiovascular disease and hyperlipidemia. It should also be conducted in the event that the total cholesterol level is high. Fasting for at least 8 hours (ideally 9 to 12 hours) prior to the test is necessary. Regular lipid profiles are required to monitor a person undergoing treatment for hypercholesterolemia, hypertriglyceridemia or hyperlipidemia.
A lipid profile measures :
- Total cholesterol
- HDL cholesterol
- LDL cholesterol
VLDL and triglycerides are important values to assess and monitor hyperlipidemia (elevated cholesterol + elevated triglycerides) or hypertriglyceridemia (elevated triglycerides but normal to low cholesterol). The reference range values for VLDL and triglycerides are discussed further under Triglycerides Levels.
HDL Cholesterol Levels (HDL-C Values and Reference Range)
- Low : less than 40 mg/dL (< 1 mmol/L) for men OR <50 mg/dL (< 1.3 mmol/L) for women
- High : greater than 60 mg/dL (< 1.55 mmol/L)
LDL Cholesterol Levels (LDL-C Values and Reference Range)
- Optimal : less than 100 mg/dL (< 2.59 mmol/L)
- Elevated but not High = 100 t 129 mg/dL (2.59 to 3.34 mmol/L)
- Borderline High = 130 to 159 mg/dL (3.37 to 4.12 mmol/L)
- High = 160 to 189 mg/dL (4.15 to 4.90 mmol/L)
- Very High : greater than 190 mg/dL (4.92 mmol/L)
The cholesterol ratio is a means of assessing a person’s risk of coronary heart disease. It uses the value of total cholesterol and HDL cholesterol but irrespective of the ratio, an elevated LDL cholesterol needs to be attended to.
The cholesterol ratio can be expressed as the ratio of the total cholesterol to HDL cholesterol. This can be done by dividing the total cholesterol value by the HDL cholesterol value. The aim is to keep the ratio below 4:1 (or quotient of 4).
- Total cholesterol = 200 mg/dL and HDL cholesterol = 50 mg/dL
- Ratio = Total cholesterol : HDL cholesterol = 200:50 = 4:1