Dyslipidaemia is a condition where the levels of fats in your blood are not in the healthy range. This includes having too much bad cholesterol, too many triglycerides, or too little good cholesterol. Because it rarely causes symptoms you can feel, getting your blood tested is the only way to know if you have it. Understanding when and how dyslipidaemia is diagnosed can help you take steps to protect your heart and overall health.

Introduction: Who Should Undergo Diagnostics and When

Dyslipidaemia often develops silently, without any noticeable signs or symptoms. Most people with high cholesterol feel perfectly well and have no idea their blood fat levels are outside the healthy range. This is why regular testing is so important, even if you feel healthy. Your doctor can check your lipid levels, which are the amounts of different types of fats circulating in your blood, through a simple blood test.^[1]

For adults aged 20 and older without existing heart problems, it is generally recommended to have your total cholesterol and HDL cholesterol (the “good” cholesterol) measured at least every five years. This helps catch any problems early before they lead to serious complications. If you are 45 years or older, your doctor may suggest having your cholesterol checked as part of a comprehensive heart health check. For people who identify as Aboriginal or Torres Strait Islander, screening should begin earlier, at age 18.^[3]

Certain groups of people need more frequent testing or should be tested earlier in life. If you have risk factors for heart disease, your doctor may want to check your lipid levels more often. These risk factors include having a family history of high cholesterol or early heart disease, being overweight or obese, having diabetes, having high blood pressure, or smoking cigarettes. People who already have heart disease, have had a heart attack or stroke, or have other conditions affecting blood vessels also need regular monitoring.^[4]

If you have been diagnosed with certain medical conditions that can affect your cholesterol levels, you should also be tested. Conditions like diabetes, chronic kidney disease, thyroid problems, or liver disease can all cause secondary dyslipidaemia, which means the abnormal lipid levels are caused by another health problem rather than inherited factors.^[1]

It is also advisable to seek testing if you notice any unusual physical signs that might suggest very high cholesterol. These can include small yellowish deposits around the eyelids, a whitish ring around the colored part of the eye in younger people, or yellowish bumps on the skin, particularly on the knuckles, elbows, or knees. However, most people with dyslipidaemia will not have any visible signs at all.^[2]

Diagnostic Methods for Identifying Dyslipidaemia

The primary tool for diagnosing dyslipidaemia is a blood test called a lipid profile or lipid panel. This test measures the levels of different types of fats in your bloodstream. Your doctor will take a sample of your blood, usually from a vein in your arm, and send it to a laboratory for analysis. The results will show several important numbers that help your healthcare team understand your heart disease risk.^[1]

The lipid profile typically includes four main measurements. The first is your total cholesterol level, which is the sum of all the cholesterol in your blood. For adults aged 20 and older, a total cholesterol level below 200 milligrams per deciliter is considered desirable. Levels between 200 and 239 are borderline high, and anything at or above 240 is considered high. However, your total cholesterol number alone does not tell the whole story, so doctors look at the individual components as well.^[3]

The second measurement is LDL cholesterol, often called “bad” cholesterol. LDL stands for low-density lipoprotein, and this is the type of cholesterol that can build up in the walls of your arteries, forming deposits called plaque. Too much plaque can narrow or block your arteries, leading to heart attacks and strokes. For most people, an LDL level below 100 milligrams per deciliter is considered optimal. Levels between 100 and 129 are considered near optimal, 130 to 159 is borderline high, 160 to 189 is high, and anything above 190 is very high. However, treatment goals for LDL can vary depending on your individual risk factors.^[5]

The third important number is HDL cholesterol, or “good” cholesterol. HDL stands for high-density lipoprotein, and this type of cholesterol actually helps remove bad cholesterol from your blood vessels and carries it back to your liver, where it can be broken down. Higher levels of HDL are generally better for your heart health. For men, an HDL level below 40 milligrams per deciliter is considered too low and increases heart disease risk. For women, the threshold is higher: levels below 50 milligrams per deciliter are considered too low. An HDL level of 60 or above is considered protective against heart disease.^[2]

The fourth component of the lipid profile is triglycerides. These are another type of fat in your blood that comes from the calories you eat but do not burn right away. Your body stores triglycerides in fat cells and releases them as energy when needed. However, if you regularly eat more calories than you burn, especially from high-fat and high-sugar foods, triglycerides can build up in your blood. Normal triglyceride levels are below 150 milligrams per deciliter. Levels between 150 and 199 are borderline high, 200 to 499 are high, and 500 or above is considered very high.^[2]

In many cases, you will be asked to fast before your lipid panel test. This means not eating or drinking anything except water for about 9 to 12 hours before the blood draw. Fasting helps ensure accurate triglyceride measurements, as eating can temporarily raise triglyceride levels. However, some newer testing guidelines allow for non-fasting tests, which can be more convenient. Your doctor will tell you whether you need to fast before your test.^[14]

In addition to the standard lipid panel, your doctor may calculate other values that help assess your cardiovascular risk. One of these is the non-HDL cholesterol level, which is calculated by subtracting your HDL level from your total cholesterol. This number represents all the “bad” types of cholesterol in your blood, including LDL and other harmful particles. Some research suggests that non-HDL cholesterol may be a better predictor of heart disease risk than LDL alone.^[4]

Before diagnosing primary dyslipidaemia, which is inherited and caused by genetic factors, your doctor will want to rule out secondary causes. Secondary dyslipidaemia occurs when lipid abnormalities are caused by other conditions or lifestyle factors. Your doctor may order additional blood tests to check for conditions like diabetes, thyroid problems, kidney disease, or liver disorders, all of which can affect cholesterol levels. They will also ask about your medications, alcohol use, and diet, as these can all influence lipid levels.^[1]

In some cases, particularly when very high cholesterol levels are found in young people or when there is a strong family history of early heart disease, genetic testing may be considered. Conditions like familial hypercholesterolaemia are inherited disorders that cause extremely high LDL cholesterol levels from birth or early childhood. Identifying these genetic conditions is important because they require more aggressive treatment to prevent early heart attacks and strokes.^[2]

Your doctor will interpret your lipid profile results in the context of your overall health and risk factors. They will consider your age, sex, blood pressure, smoking status, family history, and whether you have conditions like diabetes or existing heart disease. All of these factors together help determine your overall risk of developing cardiovascular disease and guide decisions about whether you need treatment beyond lifestyle changes.^[6]

Diagnostics for Clinical Trial Qualification

When researchers study new treatments for dyslipidaemia in clinical trials, they use specific diagnostic tests and criteria to determine which patients can participate. These enrollment criteria help ensure that the study participants are appropriate for testing the particular treatment being investigated and that the results will be meaningful and applicable to real-world patients.

The standard lipid profile test is the foundation for qualifying patients for dyslipidaemia clinical trials. Researchers typically set specific cutoff values for LDL cholesterol, total cholesterol, triglycerides, or HDL cholesterol that participants must meet to be eligible. For example, a trial testing a new cholesterol-lowering medication might require participants to have LDL cholesterol levels above 160 milligrams per deciliter, or above 130 with at least one additional cardiovascular risk factor.^[1]

In addition to baseline lipid levels, clinical trials often require documentation of whether patients have already tried standard treatments. Many trials studying new medications will only enroll patients who have not achieved their cholesterol goals despite taking existing medications like statins, or who cannot tolerate standard treatments due to side effects. This ensures the trial tests the new treatment in patients who truly need alternative options.^[7]

Clinical trials typically require multiple lipid measurements taken at different times to confirm that abnormal levels are consistent rather than temporary fluctuations. A patient might need to have two or three lipid panel tests showing elevated LDL cholesterol over several weeks or months before being considered eligible. This helps ensure that the diagnosis is accurate and stable.^[5]

Many clinical trials also require additional cardiovascular risk assessment beyond just lipid levels. Researchers may use tests like coronary calcium scoring, which measures the amount of calcium buildup in the coronary arteries, or carotid ultrasound, which looks at plaque in the neck arteries. These imaging tests help identify patients at higher risk for cardiovascular events who might benefit most from new treatments.^[8]

For trials studying inherited forms of dyslipidaemia, genetic testing may be required for enrollment. Patients with conditions like familial hypercholesterolaemia may need to provide documentation of genetic mutations or meet clinical diagnostic criteria, such as having extremely high LDL levels along with a family history of early heart disease or visible signs of cholesterol deposits.^[4]

Clinical trials typically exclude patients with certain other medical conditions that could interfere with the study or pose safety risks. Researchers usually require blood tests to check liver function, kidney function, and thyroid hormone levels before enrollment. Patients with severe liver disease, kidney failure, or uncontrolled thyroid problems are often excluded because these conditions can affect how the body processes lipids and medications.^[9]

Throughout a clinical trial, participants undergo regular lipid testing to monitor how their levels respond to the treatment being studied. These follow-up tests are typically done at scheduled intervals, such as every 4 to 12 weeks, depending on the study design. This ongoing monitoring helps researchers understand both the effectiveness and safety of the treatment over time.^[13]