LDL Cholesterol Calculator

LDL is called "bad cholesterol" because: (1) It contributes to atherosclerosis by depositing in arterial walls; (2) It triggers inflammation, attracting immune cells to form plaques; (3) It causes vascular narrowing as plaques grow; (4) It can lead to thrombosis when plaques rupture, causing heart attacks or strokes; (5) There is a dose-response relationship - higher LDL levels mean higher cardiovascular risk. In contrast, HDL can remove cholesterol from arterial walls and is therefore called "good cholesterol".

Lowering LDL cholesterol requires comprehensive management: Lifestyle changes: (1) Diet: Reduce saturated and trans fats, increase dietary fiber; (2) Exercise: At least 150 minutes of moderate-intensity aerobic exercise per week; (3) Weight: Weight loss can lower LDL; (4) Smoking cessation: Quitting improves lipid profile. Medications: (1) Statins: First-line drugs, can lower LDL by 25-50%; (2) Ezetimibe: Adjunctive therapy for further LDL reduction; (3) PCSK9 inhibitors: Potent lipid-lowering drugs; (4) Bile acid sequestrants: Older lipid-lowering drugs. Treatment should be guided by a physician based on individual risk.

Direct LDL measurement should be performed in these situations: (1) Triglycerides > 400 mg/dL (4.52 mmol/L); (2) Type III hyperlipidemia (familial dysbetalipoproteinemia); (3) Poor fasting status or non-fasting state; (4) When accurate LDL assessment is needed (such as treatment monitoring); (5) Other conditions affecting formula accuracy. Direct LDL measurement (such as homogeneous method or ultracentrifugation) is more accurate but more expensive, not suitable for routine screening.

Traditionally, 8-12 hours of fasting was required before lipid testing because eating affects triglyceride levels. However, the latest guidelines suggest: (1) Non-fasting testing is acceptable for routine screening; (2) LDL calculation may be less accurate when triglycerides are elevated in non-fasting state; (3) Triglycerides increase significantly in non-fasting state; (4) Total cholesterol and HDL are less affected by eating. Recommendation: If using Friedewald formula to calculate LDL, fasting testing is preferred. If LDL is measured directly, non-fasting testing is also acceptable.

LDL target values should be determined based on cardiovascular risk stratification: (1) Very high risk: LDL < 70 mg/dL (1.81 mmol/L), or even < 55 mg/dL (1.42 mmol/L); (2) High risk: LDL < 100 mg/dL (2.59 mmol/L); (3) Moderate risk: LDL < 130 mg/dL (3.36 mmol/L); (4) Low risk: LDL < 160 mg/dL (4.14 mmol/L). "Lower is better"? For very high-risk patients, studies show that lowering LDL to 50 mg/dL or even lower is safe and can further reduce cardiovascular event risk. However, target values should be determined by physicians based on individual patient circumstances.

The Friedewald formula has several important limitations: (1) High triglycerides: Formula is inaccurate when TG > 400 mg/dL (4.52 mmol/L); (2) Type III hyperlipidemia: Formula does not apply to these patients; (3) Non-fasting status: Ideally should be measured after 12 hours fasting; (4) Estimation nature: This is an empirical formula, direct measurement is more accurate; (5) Individual variation: The formula assumes a fixed ratio, but actual VLDL composition varies. For accurate clinical decision-making, especially when triglycerides are elevated, direct LDL measurement is recommended.