When we have a routine blood test, cholesterol is often one of the things we look at. You may be told that your cholesterol is too high, that your LDL cholesterol needs to come down, or that your HDL cholesterol is reassuringly good.
But have you ever been told about your lipoproteins or apolipoproteins?
These are terms you may not have come across before, yet they are becoming increasingly important in our understanding of cardiovascular health and the risk of heart attacks and strokes.
As a GP, I think it is worth explaining what they mean, why they matter and whether there are additional blood tests that might help us understand our individual risk more accurately.
First, what is the difference between cholesterol and lipoproteins?
Let's start with cholesterol itself.
Cholesterol is a fatty substance that our bodies need. It is an essential component of our cell membranes and is used to make hormones, vitamin D and bile acids, which help us digest fats.
So, cholesterol is not inherently bad. We need it to live.
The problem arises when certain types of cholesterol-carrying particles circulate in the blood in excessive amounts over time. These particles can enter the walls of our arteries and contribute to the build-up of fatty deposits. Over time, these deposits can narrow the arteries and, if they rupture and a blood clot forms, cause a heart attack or stroke.
This is where lipoproteins come in.
Cholesterol and triglycerides are fats, and they cannot travel around the bloodstream easily on their own. Our bodies therefore package them into tiny particles called lipoproteins.
Think of a lipoprotein as a little transport vehicle. It carries cholesterol and other fats through the bloodstream to where they are needed or where they can be processed and removed.
Different lipoproteins have different jobs. Some are more strongly associated with the build-up of fatty deposits in arteries than others.
And this is an important distinction: when we measure cholesterol, we are measuring the amount of cholesterol carried in certain particles. We are not necessarily measuring how many particles are circulating.
What are the different types of lipoproteins?
There are several types, but a few are particularly relevant when we are assessing cardiovascular risk.
1. LDL — low-density lipoprotein
LDL is often referred to as "bad cholesterol".
LDL particles can enter the walls of arteries, where they contribute to the build-up of fatty deposits. Over time, these deposits can cause arteries to narrow and become less flexible, increasing the risk of cardiovascular disease.
The longer someone is exposed to high levels of LDL and other cholesterol-carrying particles, the greater their risk of developing cardiovascular disease.
This is why lowering LDL cholesterol is such an important part of preventing heart attacks and strokes. Treatments such as statins have a strong evidence base demonstrating that they reduce cardiovascular events in people who are likely to benefit.
2. HDL — high-density lipoprotein
HDL is often called "good cholesterol".
HDL particles are involved in transporting cholesterol from tissues back towards the liver, where it can be processed and removed from the body.
Higher HDL cholesterol levels are often associated with lower cardiovascular risk. However, HDL is more complicated than simply being good, and a high HDL result does not cancel out the risk associated with high LDL or other harmful particles.
We also cannot assume that artificially raising HDL cholesterol will necessarily reduce the risk of heart attacks.
As with so many things in medicine, the full picture matters more than a single number.
3. VLDL and remnant particles
VLDL stands for very-low-density lipoprotein. These particles are made by the liver and carry triglycerides, another type of fat that the body uses to store and provide energy.
As VLDL particles travel through the bloodstream, they gradually lose some of their triglycerides. As a result, they become smaller particles, known as remnant particles. Some of these can eventually be converted into LDL.
These remnant particles can also contribute to the build-up of fatty deposits inside artery walls, increasing the risk of cardiovascular disease. This is particularly relevant for people with raised triglyceride levels, insulin resistance, type 2 diabetes or certain metabolic conditions.
In other words, LDL is not the only type of cholesterol-carrying particle that can contribute to cardiovascular disease.
4. Lipoprotein(a) — usually written as Lp(a)
This is one that deserves particular attention.
Lp(a) is a particle similar to LDL, but it has an additional protein attached to it called apolipoprotein(a).
Raised Lp(a) is an inherited risk factor for cardiovascular disease. It is associated with an increased risk of heart attacks, strokes and narrowing of the aortic valve, which is one of the heart's main valves.
The important thing about Lp(a) is that its level is largely determined by our genes. It can be raised even in someone who has a healthy diet, exercises regularly and has an otherwise reassuring cholesterol result.
You cannot tell whether your Lp(a) is high from your standard cholesterol test alone. It requires a separate blood test.
We will come back to why this matters shortly.
So, what exactly are apolipoproteins?
If lipoproteins are the transport vehicles carrying fats around the bloodstream, apolipoproteins are the proteins that help those vehicles function.
They provide structural support, help regulate how particles interact with cells, and act as signals that allow enzymes and receptors to recognise and process them.
Different lipoproteins carry different combinations of apolipoproteins.
There are several types, but three are particularly useful to understand.
Apolipoprotein B — ApoB
ApoB is especially important when we are thinking about cardiovascular risk.
ApoB is a structural protein found on the main types of lipoprotein particles that can contribute to the build-up of fatty deposits in arteries, including LDL, VLDL remnants and Lp(a).
Crucially, each of these particles carries one molecule of ApoB-100. This means that measuring ApoB in the blood gives us a useful estimate of the total number of these potentially harmful particles circulating.
Why is that important?
Imagine two people who both have an LDL cholesterol level of 3 mmol/L. At first glance, their results look identical.
However, the amount of cholesterol in the blood doesn't tell us how many particles are carrying it.
One person might have a smaller number of particles, each carrying more cholesterol. The other might have a much larger number of particles, each carrying less cholesterol.
Although their LDL cholesterol levels are the same, the second person may have more cholesterol-carrying particles circulating in their bloodstream.
This is where ApoB becomes useful. Measuring ApoB gives us an indication of how many of these potentially harmful particles are circulating.
A higher ApoB level can therefore indicate a greater number of particles capable of contributing to cardiovascular disease, even when LDL cholesterol appears normal or similar.
This is why ApoB can provide additional information about cardiovascular risk that an LDL cholesterol test alone may not capture.
ApoB can be particularly useful in people with raised triglycerides, type 2 diabetes, metabolic syndrome or established cardiovascular disease, although its usefulness depends on the individual clinical situation.
It does not mean that everyone needs an ApoB test, or that LDL cholesterol is no longer important. Rather, it is another tool that can help us make a more informed assessment.
Apolipoprotein A-I — ApoA-I
ApoA-I is the main structural protein associated with HDL particles.
It plays an important role in HDL function and in the transport of cholesterol away from tissues.
ApoA-I can be measured in a blood test, and lower levels are often associated with an unfavourable cardiovascular risk profile.
However, measuring ApoA-I is not routinely necessary for everyone. In everyday clinical practice, we generally use the standard lipid profile alongside other information to assess risk, with additional tests selected where they are likely to help.
Apolipoprotein(a) — apo(a)
This is the protein attached to an LDL-like particle to form lipoprotein(a), or Lp(a).
Although the names sound very similar, ApoA-I and apo(a) are different proteins with different roles.
The distinction matters because a test for ApoB, a test for ApoA-I and a test for Lp(a) are not interchangeable.
For most people, the two additional tests worth understanding are ApoB and Lp(a), because they can provide information that a routine cholesterol panel does not fully capture.
Why might a normal cholesterol result not tell the whole story?
A standard lipid profile usually includes total cholesterol, HDL cholesterol, triglycerides and LDL cholesterol, which is often calculated from the other measurements.
These are valuable tests, and they remain central to cardiovascular prevention.
However, there are situations in which the amount of cholesterol being carried by particles does not tell us exactly how many particles are circulating.
ApoB can help resolve that uncertainty by giving us an indication of the number of potentially harmful particles.
Similarly, someone can have a relatively unremarkable LDL cholesterol result but a raised Lp(a) level because of their genetic inheritance.
Neither situation means that a standard cholesterol test is useless. It means that a cholesterol result needs to be interpreted in the context of the whole person.
Age, blood pressure, smoking, diabetes, kidney disease, family history and previous cardiovascular disease all influence risk too.
A normal cholesterol result is reassuring in one respect, but it does not automatically mean that your overall cardiovascular risk is low.
Equally, a raised result does not mean that a heart attack or stroke is inevitable. It is an opportunity to understand risk and, where appropriate, do something about it.
Should you have an ApoB or lipoprotein(a) blood test?
There is no single blood test that tells us everything about cardiovascular health. The right tests depend on your medical history, family history and overall risk.
ApoB may be useful where the standard lipid profile does not fully reflect the suspected number of potentially harmful cholesterol-carrying particles. This can be particularly relevant for people with raised triglycerides, type 2 diabetes or certain metabolic conditions.
Lp(a) is different. Because levels are largely genetically determined, many current guidelines support measuring it at least once in adulthood.
It may be particularly worth discussing with a GP if you have:
A family history of heart attacks or strokes at a relatively young age.
A personal history of cardiovascular disease that seems disproportionate to your other risk factors.
A strong family history of raised Lp(a).
Other cardiovascular risk factors where a more detailed assessment could help guide treatment.
A raised result does not mean that you will definitely develop cardiovascular disease. It means that your risk may be higher than would otherwise be expected, and that it is worth considering this alongside your other risk factors.
Lp(a) does not usually need to be measured repeatedly because levels tend to remain relatively stable throughout adult life. Repeat testing may occasionally be appropriate in particular clinical circumstances.
At Shropshire Health, we offer an Extended Cholesterol and Cardiovascular Risk Profile for £145. This goes beyond a standard cholesterol test, measuring 14 markers including ApoB, ApoA-I and Lp(a), to provide a more detailed picture of your cholesterol levels and cardiovascular risk. You can find out more about the test and book here.
Can we lower ApoB and lipoprotein(a)?
This is an important distinction.
ApoB reflects the number of potentially harmful particles circulating in the blood. Treatments that reduce these particles, including statins and other lipid-lowering medicines where appropriate, can lower ApoB and help reduce cardiovascular risk.
Lifestyle changes can also make an important contribution to overall cardiovascular health, particularly through their effects on LDL cholesterol, triglycerides, blood pressure and metabolic health.
Lp(a) is more complicated because its level is largely inherited. Diet and exercise generally have little effect on Lp(a) itself.
However, identifying raised Lp(a) can help us pay closer attention to other modifiable risk factors, especially LDL cholesterol, blood pressure, smoking and diabetes.
Medicines specifically designed to lower Lp(a) are being investigated. We should not assume that lowering a laboratory measurement will necessarily improve clinical outcomes until appropriate trials demonstrate that benefit.
The important message is that identifying raised Lp(a) can help us make better-informed decisions about prevention.
How can you protect your cardiovascular health?
Regardless of whether we measure ApoB or Lp(a), the foundations of cardiovascular prevention remain important.
Understand your overall risk. Cholesterol is only one part of the picture. Blood pressure, smoking, diabetes, kidney function, age and family history all matter.
Eat a heart-healthy diet. A dietary pattern rich in vegetables, fruit, wholegrains, pulses, nuts and unsaturated fats can help improve cardiovascular health. Replacing some saturated fats with unsaturated fats can help lower LDL cholesterol.
Stay physically active. Regular physical activity supports blood pressure, insulin sensitivity, weight management and overall cardiovascular health.
Avoid smoking. Smoking substantially increases cardiovascular risk. Stopping smoking is one of the most effective steps you can take to protect your heart and blood vessels.
Treat risk factors when appropriate. For some people, lifestyle changes alone will not be enough. Medicines such as statins and other lipid-lowering treatments can substantially reduce cardiovascular risk when indicated.
A family history of early cardiovascular disease or a raised Lp(a) result may strengthen the case for earlier or more intensive prevention, depending on the individual's circumstances.
The aim is not to chase perfect numbers or order every available test. It is to identify the risks that matter and make sensible decisions based on the evidence.
My advice as a GP
Lipoproteins and apolipoproteins may sound complicated, but the underlying idea is quite straightforward.
Cholesterol is something our bodies need. Lipoproteins transport it around the bloodstream. Some of these particles can contribute to the build-up of fatty deposits in our arteries, and apolipoproteins help us understand more about the particles themselves.
ApoB gives us an indication of how many potentially harmful cholesterol-carrying particles are circulating in the blood. Lp(a) can reveal an inherited risk factor that might otherwise go undetected.
Neither test replaces a standard cholesterol profile, and neither should be interpreted in isolation. They are additional tools that can help us build a more complete picture of cardiovascular health.
If you have been told that your cholesterol is normal but have a strong family history of heart disease, it is reasonable to discuss whether further assessment, including Lp(a) testing, would be appropriate.
And if you are already taking medication to lower your cholesterol, do not stop or change it because of something you have read online. Your treatment should be based on your individual risk and discussed with your healthcare professional.
The most important thing to remember is that cholesterol is only one part of the cardiovascular risk picture. Your LDL cholesterol tells us how much cholesterol is being carried, ApoB gives us an indication of how many potentially harmful particles are circulating, and Lp(a) can identify an additional inherited risk.
Understanding these differences can help us identify risks that might otherwise be missed and make more informed decisions about prevention.
At Shropshire Health, we believe that good preventative medicine starts with understanding the evidence, asking the right questions and making informed decisions together.
Dr Serena Jones
