Cholesterol Explained: What Your Numbers Actually Mean

What Is Cholesterol

Cholesterol is a fatty substance that exists naturally in your blood. It is essential - your body uses it to build cell membranes, produce hormones, and make vitamin D. The problem arises when certain types of cholesterol are present in excess, because they can accumulate in the walls of arteries, narrowing them and increasing the risk of heart attack and stroke.

Cholesterol does not dissolve in blood and has to be carried by proteins. These combined packages are called lipoproteins, and the type of lipoprotein matters enormously. A standard cholesterol test, called a fasting lipid profile, measures several of these.

The Different Types

LDL cholesterol (low-density lipoprotein) is what most people mean when they talk about "bad" cholesterol. LDL carries cholesterol from the liver to cells around the body. When there is too much, it deposits in artery walls, forming plaques that gradually narrow and stiffen arteries - a process called atherosclerosis. High LDL is one of the most significant modifiable risk factors for heart disease.

HDL cholesterol (high-density lipoprotein) is the "good" cholesterol. HDL picks up excess cholesterol and carries it back to the liver for removal. Higher levels of HDL are protective - people with high HDL have a lower risk of heart disease. Low HDL is itself a risk factor.

Triglycerides are another type of fat in the blood, derived largely from the calories you eat and drink. Elevated triglycerides - particularly when combined with low HDL and high LDL - increase cardiovascular risk. High triglycerides are strongly associated with excess sugar and refined carbohydrates, alcohol, physical inactivity, and insulin resistance.

Total cholesterol is simply the sum of LDL, HDL, and a portion of triglycerides. On its own it gives a limited picture - someone can have a high total cholesterol that is largely made up of beneficial HDL, which is very different from the same number driven by high LDL.

What the Numbers Mean

Australian guidelines generally aim for:

• Total cholesterol below 5.5 mmol/L
• LDL cholesterol below 3.0 mmol/L for most adults (lower targets apply for those at high cardiovascular risk)
• HDL cholesterol above 1.0 mmol/L for men and above 1.2 mmol/L for women
• Triglycerides below 1.7 mmol/L (fasting)

These targets are not absolute thresholds - they need to be interpreted in the context of your overall cardiovascular risk. Someone with diabetes, a previous heart attack, or other risk factors will have lower LDL targets than someone with no other risk factors. This is why your GP considers the full picture rather than treating a single number in isolation.

What Raises Cholesterol

Both genetics and lifestyle play a role. Some people have a genetic condition called familial hypercholesterolaemia that causes very high LDL regardless of diet, and this runs in families. For most people, however, lifestyle factors are the main driver:

• A diet high in saturated fat (fatty meat, full-fat dairy, coconut oil, fried foods, many processed foods) raises LDL
• Trans fats - found in some commercially baked products and partially hydrogenated oils - raise LDL and lower HDL
• Physical inactivity lowers HDL and raises triglycerides
• Excess body weight, particularly around the abdomen, worsens the overall lipid profile
• Excess alcohol raises triglycerides significantly
• Smoking lowers HDL
• Certain medical conditions - including poorly controlled diabetes, hypothyroidism, and kidney disease - affect cholesterol levels

Lifestyle Changes That Make a Difference

Diet and lifestyle changes can meaningfully improve cholesterol, particularly for people with mildly elevated levels and no other major risk factors:

• Reduce saturated fat - swap fatty meats and full-fat dairy for leaner options, plant-based proteins, and unsaturated fats like olive oil, avocado, and nuts
• Increase fibre - soluble fibre, found in oats, legumes, fruit, and vegetables, actively lowers LDL
• Exercise regularly - aerobic exercise raises HDL and lowers triglycerides; even 30 minutes of walking most days helps
• Reduce sugar and refined carbohydrates - this has the greatest effect on triglycerides
• Limit alcohol - high triglycerides often respond dramatically to reducing alcohol intake
• Quit smoking - raises HDL and reduces overall cardiovascular risk

When Medication Is Recommended

For people with significantly elevated LDL, familial hypercholesterolaemia, or a high overall cardiovascular risk score, lifestyle changes alone are usually not sufficient. Statins are the most commonly prescribed medication for high cholesterol. They are highly effective at lowering LDL and have a strong evidence base for reducing heart attack and stroke. Modern statins are generally well tolerated - muscle aches, the most commonly reported side effect, are less common than many people believe, and changing to a different statin often resolves the problem.

Other medications are available for people who cannot tolerate statins or need additional LDL lowering. The right approach depends on your individual risk profile and is worth discussing with your GP.

When to Get Tested

Australian guidelines recommend that all adults over 45 have a cardiovascular risk assessment, which includes a fasting lipid profile. For Aboriginal and Torres Strait Islander peoples, and for people with a family history of early heart disease or known risk factors, screening should start earlier - at around 35. If you have not had your cholesterol checked and are over 40, booking in for a review is a sensible step.