High cholesterol is caused by a number of factors, some that you can control, and others that you can't. Some conditions, like diabetes, heart disease and hypothyroidism, can cause high cholesterol [sources: Lehrer, WebMD]. Many people end up with high cholesterol due to poor lifestyle choices, like eating a fatty diet, never setting foot in a gym, being overweight, smoking a pack a day or a combination of all of them. Those medications you're taking to help other ailments may be contributing to your high cholesterol. Common drugs known to raise cholesterol levels include thiazide diuretics, estrogen, corticosterioids and beta blockers.
Before you beat yourself up however, high cholesterol can be caused by things you can't change. There are those that are genetically predisposed to have a higher cholesterol level. If other people in your family have been diagnosed with high cholesterol, you may also be at risk, so be sure to inform your doctor if high cholesterol runs in your family. While it is rare, some have an inherited lipid disorder and their bodies' don't handle cholesterol the way a normal, healthy body would. [source: WebMD].
As with many conditions, prevention is the best treatment. To learn more about treating xanthomas, move on to the next page.