First of all, HDL means high-density lipoprotein, and LDL means low-density lipoprotein. Lipoprotein is a biochemical assembly which transports all hydrophobic fat molecules, such as triacyglycerols, phospholipids, cholesterol and so forth within the blood from liver to tissues.
The normal ranges of lipoprotein level in the blood are about 100-129 mg/dL. If one has a lipoprotein level lower than 100 mg/dL, it means he or she has a LDL. In this case, people will also say he or she has a "bad" cholesterol or otherwise a "good" one, which ranges from 160 to 189 mg/dL. Such being the case, an in-between reading of 130 to 159 mg/dL is thereafter called borderline high.
LDL cholesterol may cause people an increased risk of cancer as well as hermorrhagic stroke for it can build up cholesterol within the walls of blood vessels and narrow the passageways of blood. Worse still, if a clot is formed and gets struck in a narrowed vessel, a heart attack or stroke will possibly occur.
But on the other side, a HDL cholesterol is associated with relatively lower risk of heart diseases. The reason lies in that the HDL cholesterol can remove harmful cholesterol from both the blood and the vessel walls and take it to the liver for a reprocess.
If one happens to have LDL, he or she can improve the situation through exercise or losing weight. Also, if the one smokes, then quitting smoking will also help.