LDL Calculation

The Friedewald formula allows clinicians to estimate LDL based on total serum cholesterol, HDL and triglyceride levels. However, this formula is known to be inaccurate at extremely high triglyceride (> 400 mg/dL) and total cholesterol levels (Cordova, 2004). Additionally, triglycerides should only be calculated when fasting.

The Friedewald Formula provides an estimation of LDL cholesterol which can serve as a proxy for direct measure of serum cholesterol. A direct level of serum LDL should be measured if there is any question about accuracy.

LDL cholesterol = total cholesterol - HDL - (triglycerides / 5)

Classification of calculated LDL level according to the ATP III guidelines.

Classification of triglyceride level according to the ATP III guidelines.

Classification of HDL level according to the ATP III guidelines.

*HDL ≥60 mg/dL counts as a "negative" risk factor; its presence removed one risk factor from the total count.

Classification of total cholesterol level according to the ATP III guidelines.

Management Considerations

The ATP III cholesterol guidelines suggests additional steps after determining lipoprotein levels.   

1. Identify presence of clinical atherosclerotic disease and major risk factors.
2. Determine risk category.
3. Initiate therapeutic lifestyle changes (TLC) if LDL is above goal.
4. Consider adding drug therapy if LDL exceeds levels based on risk category.
5. Identify metabolic syndrome and treat, if present, after 3 months of TLC.
6. Treat elevated triglycerides.

LDL targets (mg/dL)*

*From NCEP 2004 Guidelines

^Risk Factors include:

• Diabetes
• Cigarette smoking
• HTN (BP ≥ 140/90 or on antihypertensive medication)
• Low HDL cholesterol (<40 mg/dL)
• Family history of premature CAD (CAD in male first-degree relative, or father < 55 years, or female first-degree relative or mother <65 years)

• Triglycerides should only be calculated when fasting.
• The Friedewald formula is known to be inaccurate at extremely high triglyceride (>400 mg/dL) and total cholesterol levels. A direct LDL level should be measured if there is any question about accuracy.