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Cholesterol, high

Page last reviewed: 13/07/2011

Cholesterol is a fatty substance known as a lipid. It is mostly made by the liver from the fatty foods we eat and is vital for the normal functioning of the body (see box, left). 

Having an excessively high level of lipids in your blood (hyperlipidemia) can have a serious effect on your health as it increases your risk of having a heart attack or stroke.

About cholesterol

Cholesterol is needed in the body to:

  • make up the structure of the membrane (outer layer) of every cell in the body,
  • insulate nerve fibres,
  • make hormones, such as sex hormones and steroid hormones, and
  • make bile acids, which are needed for the digestion and absorption of fats.

'Good' and 'bad' cholesterol

Cholesterol cannot travel around the body on its own because it does not dissolve in water. Instead, it is carried in your blood by molecules called lipoproteins.

The two main lipoproteins are LDL and HDL.

  • Low-density lipoprotein (LDL).LDL is the main cholesterol transporter and carries cholesterol from your liver to the cells that need it. If there is too much cholesterol for the cells to use, this can cause a harmful build-up in your blood. Too much LDL cholesterol in the blood can cause cholesterol to build up in the artery walls, leading to disease of the arteries. For this reason, LDL cholesterol is known as 'bad cholesterol', and lower levels are better.
  • High-density lipoprotein (HDL). HDL carries cholesterol away from the cells and back to the liver, where it is either broken down or passed from the body as a waste product. For this reason, it is referred to as 'good cholesterol', and higher levels are better.

The amount of cholesterol in the blood (including both LDL and HDL) can be measured with a blood test.

Your doctor or nurse may also measure your level of triglycerides. Triglycerides are the fats you use for energy and come from the fatty foods you eat. You store what you do not use in the fatty tissues of your body. Excess triglycerides in the blood also increase heart problems.

Normal cholesterol level

Blood cholesterol is measured in units called millimoles per litre of blood, often shortened to mmol/L. 

It is recommended that cholesterol levels should be less than 5mmol/L.

In the Ireland, half of all adults have a total cholesterol level of 5mmol/L or above.

Risks of high cholesterol

Evidence strongly indicates that high cholesterol levels can cause narrowing of the arteries (atherosclerosis), heart attack and stroke.

This is because cholesterol can build up in the artery wall , restricting the flow of blood to your heart, brain and the rest of your body. It also increases the chance of a blood clot developing.

Your risk of coronary heart disease (when your heart's blood supply is blocked or disrupted) rises as your blood's cholesterol level increases. Other factors, such as high blood pressure and smoking, increase this risk even more.

Who is at risk?

There are many factors that can increase your chance of having heart problems or stroke if you have high cholesterol. These are called risk factors.

  • Some risk factors, such as an unhealthy diet and smoking, can be changed by altering your lifestyle.
  • Some risk factors, such as having diabetes or high blood pressure, can be treated with medication.
  • Some risk factors, such as having a family history of stroke or heart disease, cannot be changed.

Page last reviewed: 13/07/2011

High cholesterol is not a disease but increases your risk of serious conditions such as:

  • coronary heart disease, caused by atherosclerosis (narrowing of the arteries),
  • stroke, and
  • mini-stroke (transient ischaemic attack or TIA).

You may only discover you have high cholesterol if you have symptoms of atherosclerosis (see below).

Coronary heart disease

A high level of cholesterol in your blood, together with a high level of triglycerides, can increase your risk of developing coronary heart disease.

Coronary heart disease is caused by narrowing of the arteries that supply the heart with blood. This narrowing is called atherosclerosis.

Cholesterol and other substances build up in the inner lining of an artery. This build-up, known as plaque, usually affects small- and medium-sized arteries. The flow of blood through the arteries is restricted as the space inside the artery is reduced.

Blood clots, which often happen in the coronary arteries (leading to the heart) during a heart attack, are more likely to develop when artery walls become rough due to the build-up of fatty deposits.

Symptoms of atherosclerosis can include:

  • Angina (pain in the chest or neighbouring parts of the body), caused by narrowed arteries going to the heart.
  • Leg pain when exercising, caused by narrowed arteries going to the lower limbs.
  • Blood clots and ruptured blood vessels, which can result in a stroke or mini-stroke (see below).
  • Ruptured plaques, which can lead to a blood clot forming in one of the arteries delivering blood to the heart (coronary thrombosis). If a significant amount of heart muscle is damaged, this may lead to heart attack, heart failure and death.
  • Cholesterol deposits around the eyes, in the skin or in the tendons. Yellowish deposits can form in the skin of the eyelids and white rings can form around the edge of the iris. In rare cases, hard white deposits of cholesterol form in the tendons, particularly around the knuckles or in the Achilles tendons (the back of the heel). These deposits may be seen in people with inherited high cholesterol (familial hypercholesterolaemia).

Stroke and mini-stroke

A stroke or mini-stroke, also called a TIA, occurs when the blood supply to your brain is disturbed. In the case of TIA, this goes back to normal within 24 hours.

Symptoms vary from person to person, but may include your face falling on one side, arm weakness or slurred speech. The symptoms of a mini-stroke usually get better very quickly.

Page last reviewed: 13/07/2011

A number of different factors can contribute to high blood cholesterol, including:

  • lifestyle factors,
  • treatable factors, and
  • fixed factors.

Lifestyle factors

There are numerous preventable lifestyle-related factors that can increase your risk of developing high blood cholesterol. These include:

  • Unhealthy diet. Some foods, such as liver, kidneys and eggs, contain cholesterol (known as dietary cholesterol). However, dietary cholesterol has little effect on blood cholesterol. More important is the amount of saturated fat in your diet. Foods that are high in saturated fat include red meat, meat pies and sausages, hard cheese, butter and lard, pastry, cakes, biscuits and cream, including sour cream and crème fraîche.
  • Lack of exercise or physical activity. This can increase your level of 'bad cholesterol' (LDL).
  • Obesity. If you are overweight, you are likely to have higher levels of LDL cholesterol and triglycerides, and a lower level of HDL.
  • Drinking excessive amounts of alcohol. Regularly drinking a lot of alcohol can increase your cholesterol and triglyceride levels.

Treatable factors

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

Some medical conditions, such as kidney and liver disease and an underactive thyroid gland, can also cause raised levels of cholesterol.

Fixed factors

There are a number of factors associated with high cholesterol that cannot be changed, including:

  • Family history of early heart disease or stroke. You are more likely to have high cholesterol if you have a close male relative (father or brother) aged under 55 or a female relative (mother or sister) aged under 65 who has had coronary heart disease or stroke.
  • A family history of a cholesterol-related condition, for example if a close relative, such as a parent, brother or sister, has familial hypercholesterolaemia (see box, right).
  • Age. The older you are, the greater your likelihood of developing atherosclerosis.
  • Ethnic group. People who are of Indian, Pakistani, Bangladeshi or Sri Lankan descent have an increased risk of high blood cholesterol.

If you have a fixed risk factor (or a number of fixed risk factors), it is even more important to address any lifestyle risk factors or treatable risk factors that you may have.


Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Thyroid gland
The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.
Obesity is when a person has an abnormally high amount of body fat.
The heart is a muscular organ that pumps blood around the body.


Triglycerides are another type of fatty substance in the blood. They are produced by the liver and are also found in dairy products, meat and cooking oils. People who are overweight, eat a diet high in fatty or sugary foods or drink a large amount of alcohol have an increased risk of having a high triglyceride level.

Page last reviewed: 13/07/2011

Blood cholesterol levels are measured with a simple blood test. You may be asked not to eat for 12 hours before the test (usually including when you are asleep at night). This ensures that all food is completely digested and will not affect the outcome of the test.

Your GP or practice nurse can carry out the blood test and will take a blood sample either using a needle and a syringe or by pricking your finger.

This blood sample will be used to determine the amount of LDL (bad cholesterol), HDL (good cholesterol) and triglycerides (other fatty substances) in your blood.

Blood cholesterol is measured in units called millimoles per litre of blood (mmol/L). In Ireland it is recommneded that your total blood cholesterol level should be less than 5mmol/L, and your level of LDL cholesterol should be under 3mmol/L.

Who should be tested?

Anyone can have their blood cholesterol level tested, but it is particularly important to have it checked if:

  • You have been diagnosed with coronary heart disease, stroke or mini-stroke or you have leg artery disease.
  • You are over 40.
  • You have a family history of early cardiovascular disease (for example, if your father or brother developed heart disease or had a heart attack or stroke before the age of 55, or if your mother or sister had these conditions before the age of 65).
  • A close family member has a cholesterol-related condition, such as familial hypercholesterolaemia (inherited high cholesterol).
  • You are overweight or obese.
  • You have high blood pressure or diabetes.
  • You have another medical condition such as a kidney condition, an underactive thyroid gland or an inflamed pancreas (pancreatitis). These conditions can cause increased levels of cholesterol or triglycerides.

Assessing your risk

When assessing your risk of heart attack or stroke, your doctor or nurse may refer to your cholesterol ratio. This is your total cholesterol level divided by your level of HDL cholesterol.

Cholesterol levels or cholesterol ratio should not be looked at on their own. A number of other factors should be taken into consideration when assessing your risk, including: 

  • BMI (body mass index), which measures your weight in relation to your height.
  • Treatable risk factors, such as high blood pressure (hypertension), diabetes and other medical conditions.
  • Your age, sex, family history and ethnicity.

At the end of your assessment, you will be told whether you have a high, moderate of low risk of getting cardiovascular disease (heart disease or stroke) within the next 10 years.


Familial is when a non-inherited disease or condition tends to affect members of the same family more than other families in the general population.

Page last reviewed: 13/07/2011

If you have been diagnosed with high cholesterol, the first method of treatment will usually involve making some changes to your diet (adopting a low-fat diet) and doing plenty of regular exercise.

After a few months, if your cholesterol level has not dropped, you will usually be advised to take cholesterol-lowering medication.


Eating a healthy diet that is low in saturated fats can reduce your level of LDL (bad cholesterol).

A healthy diet includes foods from all of the different food groups:

  • carbohydrates (cereals, wholegrain bread, potatoes, rice and pasta)
  • proteins (lean meat, beans and fish)
  • unsaturated fats
  • fruit and vegetables (at least five portions a day)

You should try to avoid or cut down on the following foods, which are rich in saturated fat:

  • fatty cuts of meat and meat products, such as sausages and pies
  • butter, ghee and lard
  • cream, soured cream, creme fraiche and ice cream
  • cheese, particularly hard cheese
  • cakes and biscuits
  • chocolate
  • coconut oil, coconut cream and palm oil

Guidelines would suggest that:

  • the average man should have no more than 30g saturated fat a day
  • the average woman should have no more than 20g saturated fat a day

To get an idea how much saturated food you are consuming, take a look at the food labels of the foods you are eating.

Cholesterol-lowering medication

There are several different types of cholesterol-lowering medication which work in different ways. Your GP can advise you about the most suitable type of treatment.

Commonly prescribed medication is outlined below.


Statins block the enzyme (a type of chemical) in your liver that is needed to make cholesterol, and reduce your blood cholesterol level.

You will usually be started on the drug simvastatin (Zocor). Other statins include atorvastatin (Lipitor) and rosuvastatin (Crestor).

When a person has side effects from using a statin, this is described as 'intolerance'. Side effects include muscle pain and stomach problems.

You usually need to take statins for life as cholesterol levels start to rise again once you stop taking them.


A low daily dose of aspirin may be prescribed, depending on your age (children under 16 should not take aspirin) and a number of other factors.

Low-dose aspirin can prevent blood clots from forming. .


Niacin is a B vitamin that is found in foods and multivitamin supplements. In high doses (available by prescription), niacin lowers LDL and triglycerides and raises HDL. However, it can cause side effects, particularly flushing (turning red in the face), so is not commonly used.

Other medications

Ezetimibe is a medication that blocks the absorption of cholesterol from food and bile juices in your intestines into your blood. It is generally not as effective as statins, but is well tolerated.

You can take ezetimibe at the same time as your usual statin, if your cholesterol levels are not low enough with the statin alone. The side effects of this combination are generally the same as those of the statin alone (muscle pain and stomach problems).

You can take ezetimibe on its own if you are unable to take a statin. This may be because you have another medical condition or you take medication that interferes with how the statin works, or because you experience side effects from statins. Ezetimibe taken on its own rarely causes side effects.

If you have high blood pressure (hypertension), your GP may also prescribe medication to lower it


Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Heart attack
A heart attack happens when there is a blockage in one of the arteries in the heart.

Omega-3 fatty acids

Many experts believe that the fats found in oily fish, called omega-3 fatty acids, are good for you. High doses can improve triglyceride levels in some patients.

Page last reviewed: 13/07/2011

You can help prevent getting high blood cholesterol by eating a healthy, balanced diet that is low in saturated fat.

Unsaturated fats

Including a small amount of unsaturated fat in your diet can be healthy as this type of fat can reduce cholesterol levels. It is thought that the traditional Mediterranean diet, with plenty of olive oil and low animal-fat content, is good for cardiovascular health (the health of the heart and blood circulation).

Foods high in unsaturated fats include:

  • oily fish
  • avocados
  • nuts and seeds
  • sunflower, rapeseed and olive oil
  • vegetable oils

Saturated fats

You should try to avoid or cut down on the following foods, which are rich in saturated fat:

  • fatty cuts of meat and meat products, such as sausages and pies
  • butter, ghee and lard
  • cream, soured cream, creme fraiche and ice cream
  • cheese, particularly hard cheese
  • cakes and biscuits
  • chocolate
  • coconut oil, coconut cream and palm oil

It is recommended that:

  • the average man should have no more than 30g saturated fat a day
  • the average woman should have no more than 20g saturated fat a day

To get an idea how much saturated food you are consuming, take a look at the food labels of the foods you are eating.

Losing weight

If you are overweight, losing weight should help reduce your cholesterol level. Regular exercise can help you lose weight.


Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
The heart is a muscular organ that pumps blood around the body.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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