LDL Cholesterol — Friedewald Equation
Calculates LDL cholesterol using the Friedewald equation when direct LDL not available. LDL = Total Cholesterol − HDL − (Triglycerides ÷ 2.2) in mmol/L. Valid only when triglycerides <4.5 mmol/L. Inaccurate in hypertriglyceridaemia, type III hyperlipidaemia, or non-fasting samples.
Score interpretation
LDL <1.8 mmol/L — optimal; target for high/very-high cardiovascular risk
→ Optimal LDL level; continue current management; confirm lifestyle; if on statin, continue and monitor lipids annually; if not on statin and at high CV risk, discuss statin therapy
LDL 1.8–2.59 mmol/L — near optimal
→ Near-optimal LDL; lifestyle optimisation (diet, exercise); statin indicated if QRISK3 ≥10% or if established CVD; target LDL <1.8 mmol/L for very high risk, <2.5 mmol/L for high risk; reassess lipids annually
LDL 2.6–3.34 mmol/L — borderline high
→ Calculate QRISK3; if ≥10% 10-year risk: high-intensity statin (atorvastatin 20–80 mg); dietary review; screen for FH (Dutch Criteria if LDL >4.9); repeat lipids in 3 months on statin; monitor LFT at 3 months
LDL 3.35–4.89 mmol/L — high LDL
→ Screen for secondary causes (hypothyroidism, nephrotic syndrome, diabetes, EtOH); high-intensity statin regardless of QRISK3; consider FH screening (Dutch Criteria); target ≥50% LDL reduction from baseline or <2.5 mmol/L; add ezetimibe if target not met on maximal statin; PCSK9 inhibitor if FH or very high CVD risk and inadequate response
LDL ≥4.9 mmol/L — very high; familial hypercholesterolaemia (FH) must be excluded
→ Screen for FH using Dutch Lipid Clinic Network Criteria or Simon Broome criteria; refer to lipid clinic; cascade screen first-degree relatives; high-intensity statin + ezetimibe; consider PCSK9 inhibitor (alirocumab or evolocumab) if targets not met; Lp(a) measurement; exclude secondary causes; annual review of lipids, LFT, CK
Interpretation bands for the LDL Calculated. Apply clinical judgement and local guidance.
References
- Friedewald WT et al. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;18(6):499–502.
Related
Curated clinical cross-links plus same-class fallbacks.
- Simvastatin · Lipid-Lowering Agent (Statin)
- Atorvastatin (CKD Cardiovascular Risk) · Cardiovascular Risk in CKD
- Icosapent Ethyl (Omega-3 — Cardiovascular Risk Reduction) · Omega-3 Fatty Acid (Purified EPA — Eicosapentaenoic Acid Ethyl Ester)
- Lipid Emulsion 20% (Intralipid) · Antidote / Resuscitation
- Insulin (IV Infusion — ICU Glucose Control) · Insulin — ICU Glucose Management
- Sodium Chloride 3% (Hypertonic Saline) · Hypertonic Electrolyte Solution — ICP/Hyponatraemia Management
- Falls Assessment in Older Adults · NICE CG161 2013
- Anaemia Investigation · BSH / NICE
- Lower Respiratory Tract Infection (Primary Care) · NICE NG138 / NICE antimicrobial guidance
- Hypertension Management · NICE NG136 2019
- Acute Heart Failure · ESC 2021 Heart Failure Guidelines; NICE NG106
- NSTEMI / Unstable Angina · ESC 2020 NSTEMI Guidelines; NICE NG185
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.