1LDL Calculation Formulas
Friedewald (mmol/L): LDL = TC − HDL − (TG ÷ 2.2)
Non-HDL Cholesterol = TC − HDL
(Non-HDL includes LDL + VLDL + IDL — better predictor in hypertriglyceridaemia)
LDL Statin Targets — AHA/ACC 2019
| Risk Category | LDL Target (mg/dL) | LDL Target (mmol/L) | Statin Intensity |
|---|---|---|---|
| Very High Risk (ASCVD, diabetes + ≥2 major risk factors, LDL >190) | <55 | <1.4 | High-intensity ± ezetimibe ± PCSK9i |
| High Risk (10-year ASCVD ≥20%, or diabetes 40–75y) | <70 | <1.8 | High-intensity statin |
| Intermediate Risk (10-year ASCVD 7.5–20%) | <100 | <2.6 | Moderate-intensity statin |
| Low Risk (<7.5% 10-year ASCVD, LDL <190) | <130 | <3.4 | Lifestyle first; statin if LDL ≥160+ |
| Familial Hypercholesterolaemia (LDL >190) | <100 (<70 if ASCVD) | <2.6 | High-intensity statin — always treat |
When Friedewald Formula is INACCURATE
- TG >400 mg/dL (4.5 mmol/L): Friedewald substantially underestimates LDL. Use direct LDL measurement or Martin-Hopkins formula (validated up to TG 800 mg/dL)
- Non-fasting sample: TG is elevated after meals, making the VLDL estimate incorrect. Always request a fasting lipid panel (12-hour fast, water allowed)
- Type III hyperlipoproteinaemia (dysbetalipoproteinaemia): Unusual VLDL composition means TG/5 overestimates VLDL — use direct LDL
- Very low LDL (<70 mg/dL): Friedewald can give falsely low or even negative values. Martin-Hopkins or direct LDL preferred
High-Intensity Statin Options (India)
- Atorvastatin 40–80 mg OD: Reduces LDL by 49–60%. Most widely used high-intensity statin in India. Available as generic
- Rosuvastatin 20–40 mg OD: Reduces LDL by 52–63%. Preferred in CKD, Asian patients (lower dose for equivalent effect). Less CYP3A4 metabolism than atorvastatin
- Ezetimibe 10 mg OD (add-on): Reduces LDL by additional 15–25%. IMPROVE-IT trial: adds 6% relative CVD risk reduction on top of statin. First-line add-on if statin alone insufficient
- PCSK9 inhibitors (evolocumab/alirocumab): Reduce LDL by 50–60% on top of statin. Expensive in India. Reserved for FH, very high-risk patients not at goal on statin + ezetimibe
2Frequently asked questions
What is the Friedewald formula for LDL?
LDL cholesterol (mg/dL) = Total Cholesterol − HDL − (Triglycerides / 5). This is valid only when fasting triglycerides are <400 mg/dL. In SI units: LDL (mmol/L) = Total Cholesterol − HDL − (Triglycerides / 2.2). The formula underestimates LDL at high triglyceride levels — use direct LDL measurement if TG >400 mg/dL.
What is the LDL target for cardiovascular risk reduction?
ACC/AHA and ESC guidelines: Very high risk (established CVD, DM with organ damage): LDL <55 mg/dL (<1.4 mmol/L). High risk (DM without organ damage, 10-year risk >10%): LDL <70 mg/dL (<1.8 mmol/L). Moderate risk: LDL <100 mg/dL (<2.6 mmol/L). Low risk: LDL <116 mg/dL (<3.0 mmol/L). More aggressive targets are recommended after recent ACS.
Which statin achieves the most LDL reduction?
High-intensity statins: atorvastatin 40–80 mg (reduces LDL ~50%) or rosuvastatin 20–40 mg (reduces LDL ~55%). Moderate-intensity: atorvastatin 10–20 mg, rosuvastatin 5–10 mg, simvastatin 20–40 mg (reduces LDL ~30–50%). Each doubling of statin dose reduces LDL by an additional ~6% ('rule of 6'). If LDL target not achieved: add ezetimibe (further ~20% reduction) before escalating to PCSK9 inhibitors.
When is the Friedewald formula inaccurate?
Inaccurate when: TG >400 mg/dL (severely hypertriglyceridaemic), TG <150 mg/dL (underestimates LDL), in type III hyperlipidaemia (dysbetalipoproteinaemia), in non-fasting samples. In these situations, use direct LDL measurement by laboratory or the Sampson-NIH equation which is more accurate at extremes of TG and LDL values.
What is nonHDL cholesterol and when is it useful?
Non-HDL cholesterol = Total Cholesterol − HDL. It includes all atherogenic lipoproteins (LDL, VLDL, IDL, Lp(a)) and is a better predictor of CVD risk than LDL alone, particularly in patients with hypertriglyceridaemia or diabetes. Non-HDL targets are typically 30 mg/dL higher than LDL targets. Non-HDL cholesterol does not require fasting and can be calculated from a random sample — useful in population screening.
Are statins safe longterm?
Statins are among the most studied drugs in medicine. Proven safe for long-term use in the vast majority. Main adverse effects: myalgia (5–10%, often non-specific), myositis with elevated CK (rare, <0.1%), rhabdomyolysis (very rare, 1–3 per 100,000). Slight increase in diabetes risk (~10% relative increase). No credible evidence for cognitive impairment or cancer risk. Routine monitoring: LFTs only if symptomatic; CK only if myalgia. Benefits far outweigh risks in patients with CVD risk.
Medical disclaimer: This calculator is for educational and clinical decision-support purposes only. It does not replace clinical judgment or specialist consultation. RxMedCalc is not liable for clinical decisions made solely on this tool.