1. Basic Knowledge of Blood Lipids

Blood lipids refer collectively to cholesterol, triglycerides (TG), and lipid-like substances (such as phospholipids and glycolipids) present in blood serum. They are widely distributed throughout the human body. Since lipids are insoluble in water, they must bind with apolipoproteins to form lipoproteins before they can be transported in the bloodstream. Blood lipids are essential substances required for the basic metabolism of living cells. Triglycerides participate in energy metabolism, while cholesterol is primarily used in the synthesis of cell membranes, steroid hormones, and bile acids.

2. Reference Values and Clinical Significance of Blood Lipid Indicators

I. Total Cholesterol (TC)

Reference Values

Desirable level: ≤ 5.2 mmol/L (200 mg/dL)

Borderline high: 5.2–6.2 mmol/L (200–240 mg/dL)

High: ≥ 6.2 mmol/L (240 mg/dL)

Clinical Significance

Elevated TC

Risks: Elevated total cholesterol increases the risk of atherosclerotic cardiovascular and cerebrovascular diseases, including coronary heart disease (CHD), myocardial infarction, and stroke.

Physiological factors contributing to elevated TC:

High-fat diet

Smoking

Alcohol consumption

Stress

Hemoconcentration

TC levels may rise significantly during the last three months of pregnancy and generally return to normal after childbirth.

Decreased TC

Low TC levels may be observed in:

Various lipoprotein deficiency disorders

Liver cirrhosis

Malignant tumors

Malabsorption syndromes

Megaloblastic anemia

Women may also experience lower TC levels during menstruation.

II. Triglycerides (TG)

Reference Values

Desirable level: < 1.7 mmol/L (150 mg/dL)

Borderline high: 1.7–2.3 mmol/L (150–200 mg/dL)

High: ≥ 2.3 mmol/L (200 mg/dL)

Clinical Significance

Elevated TG

Triglycerides are an important risk factor for coronary heart disease. Elevated TG levels should be managed through dietary modification and, when necessary, pharmacological treatment.

Decreased TG

Low TG levels may be seen in:

Hypolipoproteinemia

Malabsorption disorders

Hyperthyroidism

Prolonged fasting

Excessive physical exercise

III. High-Density Lipoprotein Cholesterol (HDL-C)

Reference Values

Desirable level: ≥ 1.0 mmol/L (40 mg/dL)

Low level: ≤ 1.0 mmol/L (40 mg/dL)

Clinical Significance

HDL-C is commonly known as the "good cholesterol" because it transports excess free cholesterol from peripheral tissues back to the liver for metabolism and excretion. This process reduces cholesterol deposition in tissues and helps protect against atherosclerosis.

Individuals with low HDL-C levels have a higher risk of developing coronary heart disease, whereas those with higher HDL-C levels generally have a lower risk.

IV. Low-Density Lipoprotein Cholesterol (LDL-C)

Reference Values

Desirable level: ≤ 3.4 mmol/L (130 mg/dL)

Borderline high: 3.4–4.1 mmol/L (130–160 mg/dL)

High: ≥ 4.1 mmol/L (160 mg/dL)

Clinical Significance

Elevated LDL-C

Elevated LDL-C is one of the most important risk factors for atherosclerosis and is widely used to assess the risk of coronary heart disease. It is also the primary target in the prevention and treatment of dyslipidemia.

Decreased LDL-C

Low LDL-C levels may be associated with:

Abetalipoproteinemia

Hyperthyroidism

Malabsorption disorders

Liver cirrhosis

Malignant tumors

V. Lipoprotein(a) [Lp(a)]

Reference Values

10–140 mmol/L (0–300 mg/L)

Pathologically elevated: ≥ 300 mg/L

Clinical Significance

Elevated Lp(a) levels increase the risk of atherosclerosis and arterial thrombosis. Increased Lp(a) concentration is recognized as an independent risk factor for atherosclerotic cardiovascular disease (ASCVD).

VI. Apolipoprotein A (ApoA)

Reference Values

1.20–1.60 g/L

Clinical Significance

Under normal circumstances, ApoA-I is a good indicator of HDL levels and is strongly positively correlated with HDL-C.

Individuals with ApoA levels below 1.20 g/L are more likely to develop coronary heart disease than those with levels above 1.60 g/L.

VII. Apolipoprotein B (ApoB)

Reference Values

0.80–1.20 g/L

Clinical Significance

ApoB primarily reflects LDL levels and is significantly positively correlated with LDL-C.

Elevated ApoB is an important risk factor for coronary heart disease. Individuals with ApoB levels above 1.20 g/L have a greater tendency to develop CHD compared with those whose levels are below 1.00 g/L. Lowering ApoB levels can reduce the incidence of coronary heart disease and promote regression of atherosclerotic plaques.

3. Blood Lipid Management

I. Lifestyle and Dietary Management

Healthy lifestyle habits and a balanced diet are fundamental to the prevention and treatment of dyslipidemia.

Factors affecting blood lipid levels include:

Diet

Physical activity

Genetic factors

Smoking

Alcohol consumption

Dietary Recommendations

A low-fat diet should emphasize:

Whole grains

Vegetables

Fruits

Foods rich in dietary fiber

These foods can help reduce LDL-C levels.

Avoid:

High-fat foods

High-salt foods

High-sugar foods

Recommended sources of high-quality protein include:

Egg whites

Lean meat

Skim milk

Foods rich in unsaturated fatty acids are also beneficial, such as:

Salmon

Sardines

Therefore, individuals with high blood lipid levels do not necessarily need to follow a vegetarian diet. The key is to eat scientifically and healthily while maintaining moderate portion sizes, ideally stopping when approximately 70–80% full.

Additional recommendations include:

Smoking cessation

Limiting alcohol consumption

Weight management

Regular physical activity

Exercise is recommended 5–7 days per week, with approximately 30 minutes of moderate-intensity activity per session. Exercise duration and intensity should be adjusted according to individual health conditions.

II. Blood Lipid Monitoring

Blood lipid levels cannot be accurately judged based on physical symptoms alone; therefore, regular monitoring is essential.

For patients receiving dietary and lifestyle interventions without medication:

Blood lipid levels should be rechecked after 3–6 months.

If target levels are achieved, non-pharmacological treatment should continue.

Follow-up testing should be conducted every 6–12 months.

Individuals with long-term stable control may undergo testing once annually.

For patients receiving lipid-lowering medication:

Blood lipid levels, liver function, and related indicators should be reassessed 4–8 weeks after treatment initiation.

If lipid goals are achieved and no special issues arise, follow-up testing may be performed every 6–12 months.

Patients with long-term stable control may be monitored annually.

If lipid targets are not achieved, adjustment of medication dosage or treatment regimen is required. Blood lipid levels should be reassessed within six weeks following any treatment adjustment.

Special Note Regarding Triglycerides

Triglyceride levels are highly influenced by dietary intake. Patients should avoid greasy or high-fat foods for at least three days before testing, as such foods may artificially elevate TG levels and affect the accuracy of clinical assessment.

III. Pharmacological Intervention

Patients are advised to consult a healthcare professional or specialized clinic to develop an individualized treatment plan and adhere to the prescribed therapy.

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