Cholesterol is different from most tests in that it is not always used to diagnose or monitor a disease but is used to estimate the risk of developing a disease, specifically cardiovascular disease. Cardiovascular disease includes heart disease (angina, heart attacks), stroke, and peripheral vascular disease (causing blocked circulation in the legs). It is due to hardening or "furring" up of the arteries (atherosclerosis), which is more likely to happen when you have a high cholesterol level. For this reason, checking your cholesterol can tell you and your doctor if you are at risk of heart disease, before you actually develop it, so you can do something about it.
To estimate your risk of cardiovascular disease, your doctor can use your cholesterol result, along with other information, into a risk calculator such as QRISK2. The value which is used in the calculator is actually your total cholesterol to HDL-C ratio, ie the balance between total cholesterol and good cholesterol.
Cholesterol is commonly tested by your GP when you reach the age of 40, as part of a routine cardiovascular health check.
It may be checked at other times if you are thought to be at increased risk of cardiovascular disease for another reason, as if this is the case, it is even more important to keep your cholesterol under control. Risk factors for cardiovascular disease 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.
Consuming excessive amounts of cholesterol and saturated fats
There is no set number which defines "normal" or "abnormal" for cholesterol. A large number of studies have shown that as your cholesterol decreases, your risk of cardiovascular disease also decreases, and in fact, there is no point where this levels off. In other words, the lower your cholesterol, the better. In the past, a total cholesterol value of less than 5.0 mmol/L was often used as a reasonable "healthy" level for most people. On the other hand, a value of less than 4.0 mmol/L was used if the person was already considered to be at higher risk of cardiovascular disease. It is likely that many people will continue using similar "targets", and indeed it is convenient to do so - but it is still worth bearing in mind that most important point is that lower the cholesterol, the better.
There is condition which runs in families called “familial hypercholesterolaemia” in which cholesterol is very high – usually over 7.5 mmol/L in adults. In fact, it is the LDL cholesterol specifically which is high. Some people, though not all, who have a cholesterol result this high, have familial hypercholesterolaemia. This is an inherited condition which is important to pick up, as if it isn’t treated there is a high risk of heart disease at a young age. Furthermore, as it is inherited, other family members might be affected. Anyone suspected of having familial hypercholesterolaemia should be referred to a specialist lipid clinic.
Cholesterol should ideally be measured when a person is healthy. It is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). To get a true representation of your cholesterol, you should wait at least six weeks after any illness before having it measured.
In women, 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 oral corticosteroids, beta blockers, oral contraceptives, thiazide diuretics, oral retinoids and phenytoin.
There has historically been some debate about whether a very low cholesterol level is harmful. Low cholesterol 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.
This article was last reviewed on 29 May 2015. | This article was last modified on 29 May 2015.
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