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Causes - High cholesterol

Cholesterol is a fatty substance found in your blood. It is vital for the normal functioning of the body. It's mainly made by the liver, but can also be found in some foods.

Having an excessively high level of cholesterol in your blood (hyperlipidemia) can have an effect on your health.

High cholesterol itself does not usually cause any symptoms, but it increases your risk of serious health conditions.

It's mainly caused by eating fatty food, not exercising enough, being overweight, smoking and drinking alcohol. It can also run in families.

Having an underlying condition, such as high blood pressure, diabetes or an underactive thyroid can also result in high cholesterol.

You can lower your cholesterol by eating healthily and getting more exercise. Some people also need to take medicine.

Too much cholesterol can block your blood vessels. It makes you more likely to have heart problems or a stroke.

Lifestyle and high cholesterol

Your lifestyle can increase your risk of developing high blood cholesterol.

Unhealthy diet

Some foods, such as liver and eggs, contain cholesterol (dietary cholesterol). But these foods have little effect on blood cholesterol. It's the total amount of saturated fat in your diet that's more important to watch.

Lack of exercise

Lack of exercise or physical activity can increase your level of "bad cholesterol" (low-density lipoprotein, or LDL).


If you're overweight or obese, you'll have higher levels of LDL cholesterol and triglycerides. You will have a lower level of high-density lipoprotein (HDL).


Regularly drinking large amounts of alcohol can increase your cholesterol and triglyceride levels.


Smoking stops "good cholesterol" (HDL) transporting cholesterol from fatty deposits to the liver. This leads to narrowing of the arteries (atherosclerosis).

Underlying conditions and high cholesterol

People with high blood pressure (hypertension) and diabetes often have high cholesterol.

Some other health conditions that can also cause raised levels of cholesterol include:

  • kidney disease
  • liver disease
  • an underactive thyroid gland (hypothyroidism)

Treating the underlying condition can help to reduce cholesterol.

Other factors linked to high cholesterol

There are some factors associated with high cholesterol that can't be changed. These increase your risk of having a heart attack or stroke. Doctors refer to these as "fixed factors".

If you have a fixed risk factor, or several fixed risk factors, it's important to look at any underlying conditions you may have which increase your risk. You may need to make some lifestyle changes.

Family history of coronary heart disease (CHD) or stroke

You're more likely to have high cholesterol if you have a close:

  • male relative under 55 who's had CHD or stroke
  • female relative under 65 who's had CHD or stroke

Family history of a cholesterol-related condition

You're more likely to have high cholesterol if you have a family history of a cholesterol-related conditions. For example, having a parent, brother or sister with high cholesterol.


The older you are, the greater the likelihood of your arteries narrowing (atherosclerosis) as deposits can build up on the walls of blood vessels over time.


Males are more likely to have heart attacks than females.

Familial hypercholesterolaemia

Familial hypercholesterolaemia is the medical term for high cholesterol that runs in families. It's caused by a gene alteration inherited from a parent, rather than an unhealthy lifestyle.

People with familial hypercholesterolaemia have raised cholesterol from birth. This can lead to the early development of heart problems, such as atherosclerosis and CHD.

Familial hypercholesterolaemia is thought to affect about 1 in 500 people.

There's a one in two (50%) chance that a child or brother or sister of someone with familial hypercholesterolaemia will also have the condition.


Triglycerides are another type of fatty substance in the blood. They're produced by the liver, and are also found in dairy products, meat and cooking oils.

An increased risk of having a high triglyceride level may be the result of:

  • being overweight
  • eating a diet high in fatty or sugary foods
  • drinking a large amount of alcohol
  • genetic factors
  • having diabetes

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 24 March 2021
Next review due: 24 March 2024

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.