Understanding Your Cholesterol Blood Test: LDL, HDL, Triglycerides

What the Lipid Panel Actually Measures

A standard lipid panel reports four values: total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. Cholesterol is a waxy lipid essential for cell membrane structure, hormone synthesis, and bile acid production. Because cholesterol is insoluble in blood, it is carried by lipoprotein particles—and it is the behaviour of those particles that determines cardiovascular risk.[3]

LDL Cholesterol: The Primary Target

LDL is commonly labelled "bad" cholesterol because elevated LDL particles can penetrate arterial walls, oxidise, and trigger atherosclerotic plaque formation.[2] Most guidelines use a calculated or directly measured LDL-C value. Optimal LDL-C is below 100 mg/dL for most adults; those with established cardiovascular disease or diabetes are typically targeted below 70 mg/dL. Near-optimal is 100–129 mg/dL, borderline high is 130–159 mg/dL, high is 160–189 mg/dL, and very high is 190 mg/dL or above.[1]

It is worth noting that LDL-C reflects cholesterol mass, not particle number. LDL particle number (LDL-P) or apolipoprotein B (ApoB) may be more predictive of risk in individuals with metabolic syndrome or insulin resistance, where LDL-C can appear normal despite a high number of small, dense particles.

HDL Cholesterol: Not Simply "Good"

HDL particles facilitate reverse cholesterol transport—removing cholesterol from peripheral tissues and returning it to the liver for excretion. An HDL-C level above 60 mg/dL is considered protective and counts as a negative risk factor in cardiovascular risk calculators. Levels below 40 mg/dL in men and below 50 mg/dL in women are associated with increased risk.[1]

However, the relationship between HDL and risk is not strictly linear. Very high HDL (above 80–90 mg/dL) does not appear to confer additional protection and in some contexts may reflect dysfunctional HDL. Lifestyle measures that raise HDL—regular aerobic exercise, smoking cessation, moderate alcohol reduction, and replacing refined carbohydrates with healthy fats—are consistently beneficial for overall cardiometabolic health.

Triglycerides: The Overlooked Marker

Triglycerides are the primary storage form of dietary fat circulating in the blood after meals. A fasting triglyceride level below 150 mg/dL is normal; 150–199 mg/dL is borderline high; 200–499 mg/dL is high; and 500 mg/dL or above is very high and carries a risk of pancreatitis. Elevated triglycerides are strongly linked to excess refined carbohydrate and sugar intake, obesity, physical inactivity, hypothyroidism, and uncontrolled diabetes.[4]

Because triglycerides rise sharply after eating, the lipid panel should always be collected after a 9–12 hour fast. Non-fasting triglycerides above 175 mg/dL are also considered elevated under more recent European guidelines.[5]

Key Ratios That Refine Risk Assessment

Individual lipid values are useful, but ratios add important context. The total cholesterol-to-HDL ratio (TC/HDL) should ideally be below 4.0; values above 5.0 indicate increasing risk. The triglyceride-to-HDL ratio (TG/HDL) is a practical proxy for insulin resistance and small dense LDL particle burden—a ratio below 2.0 (in mg/dL units) is favourable, while a ratio above 3.0 raises concern.[3]

ApoB is increasingly recommended as a single number that captures the total burden of atherogenic particles (LDL, VLDL, IDL, and Lp(a)). An optimal ApoB is below 90 mg/dL for average-risk adults and below 65–70 mg/dL for high-risk individuals.

Lifestyle Factors That Move the Numbers

Dietary saturated fat and trans fat raise LDL-C most reliably. Replacing them with monounsaturated and polyunsaturated fats lowers LDL while preserving or raising HDL. Soluble fibre from oats, legumes, and psyllium reduces LDL by binding bile acids in the gut. Weight loss of even 5–10% of body weight meaningfully lowers triglycerides and raises HDL. Regular moderate-intensity aerobic exercise—150 minutes per week or more—is one of the most effective non-pharmacological interventions.

When Medication Becomes Relevant

Statins remain the first-line pharmacotherapy for elevated LDL, with robust evidence for cardiovascular event reduction. PCSK9 inhibitors are used in high-risk patients who cannot achieve adequate LDL lowering on statins. Fibrates and omega-3 fatty acid formulations are primarily used for severe hypertriglyceridaemia. The decision to initiate medication is made alongside a formal cardiovascular risk score—such as the Pooled Cohort Equations or the SCORE2 model—rather than on a single lab value.[1]

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