Cholesterol is different from most tests in that it is not used to diagnose or monitor a disease but is used to estimate risk of developing a disease — specifically heart disease. Because high blood cholesterol has been associated with hardening of the arteries (atherosclerosis), heart disease, and a raised risk of death from heart attacks, cholesterol testing is considered a routine part of preventive health care.

Cholesterol testing is recommended as a screening test to be done on all adults at least once every five years. It is frequently done in conjunction with a routine physical exam. It is usually ordered in combination with other tests including HDL-C, LDL-C, and triglycerides — often called a lipid profile.

Cholesterol is tested at more frequent intervals (often several times per year) in patients who have been prescribed diet and/or drugs to lower their cholesterol. The test is used to track how well these measures are succeeding in lowering cholesterol to desired levels and in turn lowering the risk of developing heart disease.

Cholesterol testing may be ordered more frequently for those who have one or more risk factors for heart disease. Major risk factors include:

• Cigarette smoking
• Age (men 45 years or older or women 55 years or older)
• Hypertension (blood pressure of 140/90 or higher or taking high blood pressure medications)
• Family history of premature heart disease (heart disease in an immediate family member—male relative under age 55 or female relative under age 65)
• Pre-existing heart disease or already having had a heart attack
• Diabetes mellitus

For those under 20 years of age and at low risk, cholesterol testing is usually not ordered routinely. However, screening for high cholesterol as part of a lipid profile is recommended for children and youths who are at an increased risk of developing heart disease as adults. Some of the risk factors are similar to those in adults and include:

• Family history—history of high cholesterol or heart disease in close relatives, particularly if occurring before age 55 in women or 65 in men. If the family history is not known, a cholesterol test is recommended, especially if other risk factors are present.
• Being overweight or obese—when the youth’s body mass index (BMI) is at or above the 85th percentile, cholesterol testing is recommended. The BMI should be calculated at least once a year by the youth’s health care provider. For an obese youth (one whose BMI is at or above the 95th percentile), laboratory tests to measure cholesterol levels may be recommended every 2 years.
• Consuming excessive amounts of cholesterol, saturated fats, and trans fats
• Diabetes mellitus
• High blood pressure (hypertension)
• Smoking cigarettes

High-risk children should have their first cholesterol test between 2 and 10 years old, according to the American Academy of Pediatrics. Children younger than 2 years old are too young to be tested. If the initial results are not worrisome, the fasting test should be done again in three to five years.

For adults, in a routine setting where testing is done to screen for risk, the test results are grouped in three categories of risk:

• Desirable: A cholesterol below 200 mg/dL (5.18 mmol/L) is considered desirable and reflects a low risk of heart disease.
• Borderline high: A cholesterol of 200 to 239 mg/dL (5.18 to 6.18 mmol/L) is considered to reflect moderate risk. Your doctor may decide to order a lipid profile to see if your high cholesterol is due to the amount of bad cholesterol (high LDL-C) or good cholesterol (high HDL-C) in your blood. Depending on the results of the lipid profile (and any other risk factors you may have), your doctor will decide what to do.
• High Risk: A cholesterol greater than or equal to 240 mg/dL (6.22 mmol/L) is considered high risk. Your doctor may order a lipid profile (as well as other tests) to try to determine the cause of your high cholesterol. Once the cause is known, an appropriate treatment will be prescribed.

The risk categories for children and adolescents are different than adults. Talk to your child’s pediatrician about your child’s results.

In a treatment setting, testing is used to see how much cholesterol is decreasing as a result of treatment. The goal for the amount of change or the final (target) value will be set by your doctor. The target value is usually based on LDL-C.

Cholesterol should be measured when a person is not ill. Blood cholesterol is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait at least 6 weeks after any illness to have cholesterol measured.

There is some debate about whether very low cholesterol is bad. Low cholesterol (less than 100 mg/dL (2.59 mmol/L)) is often seen when there is an existing problem like malnutrition, liver disease, or cancer. However there is no evidence that low cholesterol causes any of these problems.

Cholesterol is high during pregnancy. Women should wait at least six weeks after the baby is born to have cholesterol measured.

Some drugs that are known to increase cholesterol levels include anabolic steroids, beta blockers, epinephrine, oral contraceptives, and vitamin D.