High cholesterol is when you have too much of a fatty substance called cholesterol in your blood.

There are two main types of cholesterol - HDL cholesterol (high density lipoprotein) and LDL cholesterol (low density lipoprotein). HDL cholesterol is called good cholesterol or healthy cholesterol, because it mops up cholesterol left behind in your arteries and carries it to your liver where it is broken down and passed out of your body. LDL cholesterol travels from your liver through your arteries to other parts of your body. LDL is called bad cholesterol because it sticks to the walls in your arteries - making them narrow. This reduces the blood supply to your heart or brain.

Having an excessively high level of LDL cholesterol in your blood (hyperlipidemia) can have an effect on your health. Too much cholesterol can block your blood vessels. It makes you more likely to have heart problems or a stroke.

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

You can only find out if you have it from a blood test.

High cholesterol is mainly caused by:

• eating fatty food

• not exercising enough

• being overweight

• smoking

• 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.

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).

Obesity

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).

Alcohol

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

Smoking

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.

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.

Fixed risk factors include:

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.

Age

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.

Gender

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.

Triglycerides

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

Getting a cholesterol test

A blood sample is taken to find the amount of bad and good cholesterol and other fatty substances in your blood.

You should not eat for 10 to 12 hours before the cholesterol test. This is to make sure that all food is digested and will not affect the outcome of the test.

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

Your GP may recommend that you have your blood cholesterol levels tested if you:

• have been diagnosed with coronary heart disease, stroke, mini-stroke or peripheral arterial disease

• are over the age of 40 – you should have your estimate of cardiovascular disease risk reviewed regularly

• have a family history of early cardiovascular disease

• have a family member who has a cholesterol-related condition, such as familial hypercholesterolaemia

• are overweight or obese

• have high blood pressure or diabetes

• have another medical condition such as, kidney disease, an under active thyroid, or an inflamed pancreas (pancreatitis). These conditions can cause increased levels of cholesterol or triglycerides

Results of cholesterol tests

After your cholesterol test, your GP or nurse will explain your results. They will calculate the risk you have of developing heart disease or stroke within the next 10 years.

This risk is not just based on your cholesterol reading.

It also takes into account:

• your BMI (body mass index) – which measures your weight in relation to your height

• treatable risk factors like high blood pressure (hypertension), diabetes and other medical conditions

• your age, sex, family history and ethnicity

Based on your results, your GP or nurse will recommend steps you can take to reduce your risk of developing cardiovascular disease.

This may include advice about making lifestyle changes. These could include eating more healthily stopping smoking and exercising more. They may also recommend cholesterol-lowering medication, such as statins.

Treatment will be recommended for you. Other members of your family who may be affected may also be tested.

You'll have a full review at least once a year to check how well your treatment is working. They will also assess any symptoms you may have.

These are various treatments for high cholesterol:

Healthy diet

Eating a healthy, balanced diet that's low in saturated fats can reduce your level of "bad cholesterol" (LDL).

If your diet is high in fat, fatty plaques are much more likely to build up in your arteries. This is because fatty foods contain cholesterol.

There are 2 types of fat: saturated and unsaturated. Avoid foods containing saturated fats. They will increase the levels of "bad cholesterol" in your blood.

Foods high in saturated fat include:

• sausages and fatty cuts of meat

• butter

• lard

• cream

• hard cheese

• cakes and biscuits

• food that contains coconut or palm oil

It's not healthy to completely cut out all types of fat from your diet. It's important to replace saturated fats with unsaturated fats. They increase levels of "good cholesterol" and reduce any blockage in your arteries.

Foods that are high in unsaturated fat include:

• oily fish – such as mackerel, salmon and tuna

• avocados

• nuts and seeds

• sunflower, rapeseed and olive oil

A low-fat diet including lots of fibre and plenty of fruit and vegetables has also been shown to help lower cholesterol.

Fruit and vegetables are full of vitamins, minerals and fibre. They help keep your body in good condition. Aim to eat five 80g portions of fruit and vegetables or 30g of fibre every day.

Plant sterols 

Plant stanols and sterols are natural chemicals found in small amounts in some plant-based foods like vegetable oils, nuts, seeds, legumes, fruit, vegetables, and wholegrains. Studies show that, along with a healthy diet, eating foods that provide you with around 2 grams of plant stanols or sterols every day can reduce LDL cholesterol (the bad cholesterol) in our blood. However, the amount we find naturally in food is not enough to lower cholesterol. Because of this, food companies developed foods with plant sterols or stanols added to them, like yogurt drinks, fat spreads, milk, and yogurts.

Plant stanols and sterols are similar in size and shape to cholesterol, so they compete with cholesterol for absorption in our intestines. This means we absorb less cholesterol from food, which helps to lower total cholesterol and LDL cholesterol in our blood. Cholesterol also gets into the digestive tract from the liver and plant stanols or sterols help to reduce the amount of this type of cholesterol you re-absorb.

Plant stanols/sterols have no effect on HDL cholesterol (the good cholesterol) or triglycerides (another fat in our blood).

Eating 2g of plant stanols or sterols every day has been shown to be generally safe and effective at reducing cholesterol by 7.5 to 12 per cent in about three weeks. However, there is no long-term evidence to show that these products reduce your risk of having a heart attack or stroke. Once you stop eating plant sterols the effect of lowering cholesterol stops. 

Stop smoking 

High-density lipoprotein (HDL) cholesterol is known as the "good" cholesterol because it helps remove other forms of cholesterol from your bloodstream.

A chemical found in cigarettes stops HDL transporting fatty deposits to the liver. This leads to high cholesterol and narrowing of the arteries (atherosclerosis). This means smoking is a major risk factor for both heart attacks and strokes.

If you decide to stop smoking, your GP can refer you to the HSE's free stop smoking service. This will provide you with dedicated help and advice about the best ways to give up smoking.

Exercise

Being active and exercising regularly will increase the levels of HDL in your body. Exercise stimulates the body to move fatty deposits to the liver, so they can be broken down.

Exercise will also help you maintain a healthy weight, and lose weight if you're overweight. Being overweight can increase the amount of "bad cholesterol" in your blood.

Physical activity will help lower your blood pressure by keeping your heart and blood vessels in good condition.

Doing 150 minutes of moderate-intensity exercise every week is recommended to help lower your cholesterol. Walking, swimming and cycling are good examples of this type of exercise.

Cut down on alcohol

Try to:

• avoid drinking more than the recommended weekly units

• have several drink-free days each week

• avoid drinking lots of alcohol in a short time (binge drinking)

Ask your GP for help and advice if you're struggling to cut down.

Cholesterol-lowering medication

There are several different types of cholesterol-lowering medication that work in different ways. Your GP can tell you about the most suitable type of treatment. They may also prescribe medication to lower high blood pressure if it affects you.

The most prescribed medications are statins and ezetimibe.

Statins

Statins block the enzyme in your liver that helps to make cholesterol. This leads to a reduction in your blood cholesterol level.

Once diagnosed with high cholesterol, you will be prescribed a statin such as atorvastatin, simvastatin, pravastatin or rosuvastatin. There are other alternatives available.

When someone has side effects from using a statin, it's described as having an "intolerance" to it.

Side effects of statins include:

• headaches

• stomach problems, such as indigestion, diarrhoea or constipation

• muscle pain

You should speak to your GP immediately if you have unexplained muscle pain, tenderness, or weakness when taking a statin.

Statins will only be prescribed to people who continue to be at high risk of heart disease. This is because they need to be taken for life. Cholesterol levels start to rise again once you stop taking them.

Ezetimibe

Ezetimibe medication blocks how cholesterol from food is absorbed into your blood. It's generally not as effective as statins, but is less likely to cause side effects.

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 the same as the statin on its own - muscle pain, headaches and stomach problems.

You can take ezetimibe by itself if you're unable to take a statin. This may be because you have another medical condition. It may also be because you take medication that interferes with how the statin works. Ezetimibe taken on its own rarely causes side effects.