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Cholesterol is found in every cell in your body. This fat-like substance is an important component of cell membranes and a building block in the formation of some hormones. But your body makes all the cholesterol it needs. Any cholesterol in your diet is extra — and it's up to no good.

When there's too much cholesterol in your blood, you may develop fatty deposits in your blood vessels. Eventually, these deposits make it difficult for enough blood to flow through your arteries. Your heart may not get as much oxygen-rich blood as it needs, which increases the risk of a heart attack. Decreased blood flow to your brain can cause a stroke.

But there's good news. High blood cholesterol (hypercholesterolemia) is largely preventable. A healthy diet, regular exercise and other lifestyle changes can go a long way toward reducing high cholesterol. Sometimes medication is needed, too.

High cholesterol has no symptoms. A blood test is the only way to detect high cholesterol.

Cholesterol is carried through your blood attached to proteins. The cholesterol-protein package is called a lipoprotein.  The main types of lipoproteins are:

• Low-density lipoprotein (LDL). LDL, or "bad," cholesterol transports cholesterol throughout your body. LDL cholesterol builds up in the walls of your arteries, making them hard and narrow.
• High-density lipoprotein (HDL). HDL, or "good," cholesterol picks up excess cholesterol and takes it back to your liver.

Various factors within your control — such as inactivity, obesity and an unhealthy diet — contribute to high LDL cholesterol and low HDL cholesterol. Factors beyond your control may play a role, too. For example, your genetic makeup may keep cells from removing LDL cholesterol from your blood efficiently or cause your liver to produce too much cholesterol.

You're more likely to have high cholesterol if you're inactive, obese or eat unhealthy foods. Although high cholesterol can lead to heart disease on its own, other factors compound the risk:

• Smoking. Cigarette smoking damages the walls of your blood vessels, making them likely to accumulate fatty deposits. Smoking may also lower your level of HDL cholesterol.
• High blood pressure. Increased pressure on your artery walls damages your arteries, which can speed the accumulation of fatty deposits.
• Diabetes. High blood sugar contributes to high LDL cholesterol and low HDL cholesterol. High blood sugar also damages the lining of your arteries.
• Family history of heart disease. If a parent or sibling developed heart disease before age 55, high cholesterol levels place you at a greater than average risk of developing heart disease.

Ask your doctor for a baseline cholesterol test when you're in your 20s and then have your cholesterol tested at least every five years. If your test results aren't within desirable ranges, your doctor may recommend more frequent measurements.

A blood test to check cholesterol levels — called a lipid panel or lipid profile — typically reports:

• Total cholesterol
• LDL cholesterol
• HDL cholesterol
• Triglycerides — a type of fat in the blood

For the most accurate measurements, don't eat or drink anything (other than water) for nine to 12 hours before the blood sample is taken.

Interpreting the numbers
Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. To interpret your test results, use these general guidelines.

LDL targets differ
Because LDL cholesterol is closely associated with heart disease, it's the main focus of cholesterol-lowering treatment. But it's not as simple as the chart may appear. Your target LDL number can vary, depending on your underlying risk of heart disease.

Most people should aim for an LDL level below 130 mg/dL. If you have other risk factors for heart disease, your target LDL may be below 100 mg/dL. If you're at very high risk of heart disease, you may need to aim for an LDL level below 70 mg/dL.

So who's considered very high risk? You might be if you've had a heart attack or if you have diabetes. In addition, two or more of the following risk factors might also place you in the very high risk group:

• Smoking
• High blood pressure
• Low HDL cholesterol
• Family history of early heart disease
• Age older than 45 if you're a man, or older than 55 if you're a woman

High cholesterol can cause atherosclerosis, a dangerous accumulation of fatty deposits on the walls of your arteries. These deposits — called plaques — can reduce blood flow through your arteries. If the arteries that supply your heart with blood (coronary arteries) are affected, you may have chest pain and other symptoms of coronary artery disease.

If plaques tear or rupture, a blood clot may form — blocking the flow of blood or breaking free and plugging an artery downstream. If blood flow to part of your heart stops, you'll have a heart attack. If blood flow to part of your brain stops, a stroke occurs.

Lifestyle changes can help improve your cholesterol level. Eat a healthy diet, get regular physical activity and avoid smoking. If you've made these important lifestyle changes and your total cholesterol — particularly your LDL cholesterol — remains high, your doctor may recommend medication.

The specific choice of medication or combination of medications depends on various factors, including your individual risk factors, your age, your current health and possible side effects. Common choices include:

• Statins. Statins — among the most commonly prescribed medications for lowering cholesterol — block a substance your liver needs to make cholesterol. This depletes cholesterol in your liver cells, which causes your liver to remove cholesterol from your blood. Statins may also help your body reabsorb cholesterol from accumulated deposits on your artery walls, potentially reversing coronary artery disease. Choicesinclude atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev, Mevacor), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor).
• Bile-acid-binding resins. Your liver uses cholesterol to make bile acids, a substance needed for digestion. The medications cholestyramine (Prevalite, Questran), colesevelam (WelChol) and colestipol (Colestid) lower cholesterol indirectly by binding to bile acids. This prompts your liver to use excess cholesterol to make more bile acids, which reduces the level of cholesterol in your blood.
• Cholesterol absorption inhibitors. Your small intestine absorbs the cholesterol from your diet and releases it into your bloodstream. The drug ezetimibe (Zetia) helps reduce blood cholesterol by limiting the absorption of dietary cholesterol. Zetia can be used in combination with any of the statin drugs.
• Combination cholesterol absorption inhibitor and statin. The combination drug ezetimibe-simvastatin (Vytorin) decreases both absorption of dietary cholesterol in your small intestine and production of cholesterol in your liver.

If you also have high triglycerides, your doctor may prescribe:

• Fibrates. The medications fenofibrate (Lofibra, Tricor) and gemfibrozil (Lopid) decrease triglycerides by reducing your liver's production of very-low-density lipoprotein (VLDL) cholesterol and by speeding up the removal of triglycerides from your blood. VLDL cholesterol contains mostly triglycerides.
• Niacin. Niacin (Niaspan) decreases triglycerides by limiting your liver's ability to produce LDL and VLDL cholesterol. Various prescription and over-the-counter preparations are available, but prescription niacin is preferred. Dietary supplements containing niacin are not effective for lowering triglycerides.

Most of these medications are well tolerated, but effectiveness varies from person to person. The most common side effects are stomach pain, constipation, nausea and diarrhea. If you decide to take cholesterol medication, your doctor may recommend periodic liver function tests to monitor the medication's effect on your liver.

Lifestyle changes are the first line of defense against high cholesterol. To promote healthy cholesterol levels, lose excess weight, eat healthy foods and increase your physical activity. If you smoke, quit.

Lose excess pounds
Excess weight contributes to high cholesterol. Losing even 5 to 10 pounds of excess weight can help lower total cholesterol levels. Start by taking an honest look at your eating habits and daily routine. Consider your challenges to weight loss — and ways to overcome them.

Eat heart-healthy foods
What you eat has a direct impact on your cholesterol level. In fact, researchers say a diet rich in fiber and other cholesterol-lowering foods may help lower cholesterol as much as statin medication for some people.

• Choose healthier fats. Saturated fat and trans fat raise your total cholesterol and LDL cholesterol. Get no more than 10 percent of your daily calories from saturated fat, and try to avoid trans fat completely. Monounsaturated fat — found in olive, peanut and canola oils — is a healthier option. Almonds and walnuts are other sources of healthy fat.
• Limit your cholesterol intake. Aim for no more than 300 milligrams (mg) of cholesterol a day — or less than 200 mg if you have heart disease. The most concentrated sources of cholesterol include organ meats, egg yolks and whole milk products. Use lean cuts of meat, egg substitutes and skim milk instead.
• Select whole grains. Various nutrients found in whole grains promote heart health. Choose whole-grain breads, whole-wheat pasta, whole-wheat flour and brown rice. Oatmeal and oat bran are other good choices.
• Stock up on fruits and vegetables. Fruits and vegetables are rich in dietary fiber, which can help lower cholesterol. Snack on seasonal fruits. Experiment with veggie-based casseroles, soups and stir-fries.
• Eat heart-healthy fish. Some types of fish — such as cod, tuna and halibut — have less total fat, saturated fat and cholesterol than do meat and poultry. Salmon, mackerel and herring are rich in omega-3 fatty acids, which help promote heart health.
• Drink alcohol only in moderation. In some studies, moderate use of alcohol has been linked with higher levels of HDL cholesterol — but the benefits aren't strong enough to recommend alcohol for anyone who doesn't drink already. If you choose to drink, do so in moderation. This means no more than one drink a day for women, and one to two drinks a day for men.

Exercise regularly
Regular exercise can help improve your cholesterol levels. With your doctor's OK, work up to 30 to 60 minutes of exercise a day. Take a brisk daily walk. Ride your bike. Swim laps. To maintain your motivation, keep it fun. Find an exercise buddy or join an exercise group.

Don't smoke
If you smoke, stop. Quitting can improve your HDL cholesterol level. And the benefits don't end there. Just 20 minutes after quitting, your blood pressure decreases. Within 24 hours, your risk of a heart attack decreases. Within one year, your risk of heart disease is half that of a smoker's. Within 15 years, your risk of heart disease is similar to that of someone who's never smoked.

Few natural products have been proved to reduce cholesterol, but some might be helpful. With your doctor's OK, consider these cholesterol-lowering supplements and products:

• Artichoke extract
• Barley
• Beta-sitosterol (found in oral supplements and some margarines, such as Take Control)
• Blond psyllium (found in seed husk and products such as Metamucil)
• Garlic extract
• Oat bran (found in oatmeal and whole oats)
• Sitostanol (found in oral supplements and some margarines, such as Benecol)

If you choose to take cholesterol-lowering supplements, remember the importance of a healthy lifestyle. If your doctor prescribes medication to reduce your cholesterol, take it as directed. Make sure your doctor knows which supplements you're taking as well.