From Jennifer Moll,
Your Guide to Cholesterol.
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About.com Health's Disease and Condition content is reviewed by Rich Fogoros, MD

When you get a lipid panel, there are three main types of cholesterol that are tested: low density lipoprotein (LDL), high density lipoprotein (HDL), and very low density lipoprotein (VLDL). Triglycerides, another type of lipid in the blood, are also tested. The amounts of each lipid in your blood will allow your health care provider to predict your risk for heart disease in the future.

Low Density Lipoproteins

Low density lipoproteins, also referred to as LDL, is known as the "bad cholesterol". LDLs are produced by the liver and carry cholesterol and other lipids (fats) from the liver to different areas of the body, like muscles, tissues, organs, and the heart. It is very important to keep LDL levels low, because high levels of LDL indicate that there is much more cholesterol in the blood stream than necessary, therefore increasing your risk of heart disease. LDLs are calculated by using an equation involving total cholesterol, triglycerides, and HDLs--all of which are measured directly in the blood:

LDL = TC – (triglycerides/5) + HDL)

The following guidelines have been set forth by the National Cholesterol Education Program:

• LDL levels less than 100 mg/dL ( 2.6 mmol/L) are considered optimal.
  
• LDL levels between 100 – 129 mg/dL (2.6–3.34 mmol/L) are considered near or above optimal.
  
• LDL levels between 130 – 159 mg/dL (3.36–4.13 mmol/L) are considered borderline high.
  
• LDL levels between 160 – 189 mg/dL (4.14 - 4.90 mmol/L) are considered high.
  
• LDL levels at or above 190 mg/dL (4.91 mmol/L) is considered very high.
  

High Density Lipoproteins

High density lipoprotein, also known as HDL, is considered the "good" cholesterol. HDL is produced by the liver to carry cholesterol and other lipids (fats) from tissues and organs back to the liver for recycling or degradation. High levels of HDL are a good indicator of a healthy heart, because less cholesterol is available in your blood to attach to blood vessels and cause plaque formation. According to the National Cholesterol Education Program:

• Any HDL level above more than 60 mg/dL (1.56 mmol/L) is considered high. A high HDL level is considered very healthy, since it has a protective role in guarding against heart disease.
  
• An acceptable HDL range is between 40- 60 mg/dL (1.04–1.56 mmol/L).
  
• An undesirable level of HDL is any level below 40 mg/dL (1.04 mmol/L). In this case, low HDL levels may help to contribute to heart disease.
  

Very Low Density Lipoproteins

Very low density lipoproteins, or VLDL, are lipoproteins that carry cholesterol from the liver to organs and tissues in the body. They are formed by a combination of cholesterol and triglycerides. VLDLs are heavier than low density lipoproteins, and are also associated with atherosclerosis and heart disease. This number is obtained by dividing your triglyceride levels by 5.

<sub>Sources
Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (PDF)

Heart Protection Study Collaborative Group. MRC/BHF heart protection study of cholesterol lowering with simvastatin in 20,536 high-risk individuals: a randomized placebo-controlled trial. Lancet 2002;360:7-22.</sub>