What is high cholesterol?
Cholesterol is a waxy, fat-like substance that your body needs to build cells and make hormones. It travels through your blood attached to proteins, forming lipoproteins. Low-density lipoprotein (LDL) is often called bad cholesterol because too much of it builds up in artery walls, while high-density lipoprotein (HDL) is called good cholesterol because it helps remove cholesterol from the blood.
High cholesterol means you have too much LDL, or too little HDL, or both. Over time, excess LDL contributes to fatty deposits called plaques that narrow and stiffen your arteries — a process called atherosclerosis — raising the risk of heart attack and stroke.
Why it matters
High cholesterol itself causes no symptoms, so many people are unaware they have it until they have a heart attack, stroke or a routine blood test. The danger lies in what it does silently over years: narrowing the arteries that supply your heart and brain. When a plaque ruptures, it can trigger a clot that blocks blood flow, causing a heart attack or stroke.
Because of this, lowering high cholesterol is one of the most effective ways to reduce cardiovascular risk, particularly when combined with managing blood pressure, blood sugar and other risk factors.
What causes high cholesterol?
High cholesterol can result from lifestyle, genetics or both. Common contributing factors include:
- •A diet high in saturated and trans fats
- •Being overweight or obese
- •Lack of physical activity
- •Smoking, which lowers HDL
- •Drinking too much alcohol
- •Increasing age
- •Family history, including an inherited condition called familial hypercholesterolaemia
- •Certain conditions such as diabetes, kidney disease and an underactive thyroid
How it's diagnosed
High cholesterol is found with a blood test called a lipid panel or lipid profile, which measures total cholesterol, LDL, HDL and triglycerides (another type of blood fat). The test is sometimes done after fasting. Your doctor interprets the numbers together with your other risk factors — such as age, blood pressure, smoking and family history — to assess your overall cardiovascular risk, rather than focusing on any single value.
The total cholesterol to HDL ratio is one useful summary measure, and there are simple tools to help you understand your numbers, though your doctor's overall assessment is what guides treatment.
How to lower cholesterol
Lifestyle changes are the first step and can meaningfully improve cholesterol. These include eating less saturated and trans fat, choosing healthy fats such as those in olive oil, nuts and oily fish, eating more fibre from vegetables, fruit, oats and beans, losing excess weight, exercising regularly, stopping smoking and limiting alcohol.
When lifestyle changes are not enough, or when cardiovascular risk is high, medication is added. Statins are the most commonly prescribed and are highly effective at lowering LDL and reducing the risk of heart attacks and strokes. Other medicines are available for those who cannot take statins or need additional lowering. Treatment decisions are based on your overall risk, not cholesterol alone.
Understanding your cholesterol numbers
A cholesterol blood test, or lipid panel, reports several numbers, and understanding them helps make sense of your result. Total cholesterol is the overall amount in your blood. LDL, the 'bad' cholesterol, is the figure most closely linked to artery-clogging and is usually the main treatment target. HDL, the 'good' cholesterol, helps remove cholesterol from the blood, so a higher level is protective.
Triglycerides are another type of blood fat, raised by excess weight, alcohol, sugary foods and inactivity. Doctors sometimes also use the total cholesterol to HDL ratio as a summary measure of risk. Crucially, there is no single 'good' number that applies to everyone: your ideal targets depend on your overall cardiovascular risk, taking into account age, blood pressure, smoking, diabetes and family history.
This is why two people with identical cholesterol readings might receive different advice. Someone at high overall risk may be advised to lower their LDL more aggressively than someone at low risk with the same number. Your doctor interprets your numbers in this fuller context rather than treating any single value in isolation.
Complications and cardiovascular risk
High cholesterol matters because of what it does silently over years. Excess LDL gradually builds up in the walls of arteries, forming fatty deposits called plaques in a process known as atherosclerosis. As plaques grow, they narrow and stiffen the arteries, restricting blood flow.
The most serious consequences occur when a plaque ruptures, triggering a blood clot that can block an artery. If this happens in an artery supplying the heart, it causes a heart attack; in an artery supplying the brain, a stroke. High cholesterol can also contribute to peripheral arterial disease, reducing blood flow to the limbs. This is why lowering cholesterol is one of the most effective ways to reduce the risk of these life-threatening events.
The good news is that this process can be slowed and the risk substantially reduced. Lifestyle changes and, where appropriate, medication such as statins lower LDL and the chance of heart attacks and strokes, particularly in those at higher overall risk.
Diet and lifestyle for healthy cholesterol
What you eat has a meaningful effect on your cholesterol, and dietary changes are a cornerstone of management. The most important step is reducing saturated fat — found in fatty cuts of meat, butter, cream, full-fat dairy, and many processed and fried foods — and replacing it with healthier unsaturated fats from sources such as olive oil, rapeseed oil, nuts, seeds and oily fish.
Increasing soluble fibre also helps, as it can reduce the absorption of cholesterol into the bloodstream. Good sources include oats, barley, beans, lentils, fruit and vegetables. Some foods are fortified with plant sterols and stanols, which can further lower LDL. Beyond diet, regular physical activity raises protective HDL cholesterol and supports a healthy weight, while stopping smoking improves HDL and overall cardiovascular health.
These changes work best together and as part of a sustained pattern rather than a short-term diet. Even when medication is needed, lifestyle measures remain valuable, often allowing better results at lower doses and improving overall heart health in ways that go beyond cholesterol numbers alone.