LDL Cholesterol (Friedewald Formula)

What the Friedewald formula estimates in the lipid panel

The Friedewald formula estimates the cholesterol carried by low-density lipoproteins (LDL) from three measured tests: total cholesterol, HDL cholesterol and triglycerides. Published by Friedewald, Levy and Fredrickson in the journal Clinical Chemistry in 1972, it rests on one premise: in the fasting state, almost all circulating triglyceride is in VLDL, which carry roughly one part cholesterol to five parts triglyceride.

With this proportion, VLDL cholesterol is estimated as triglycerides/5 (in mg/dL), and LDL is obtained by difference. The result is called calculated LDL, to distinguish it from LDL measured by a direct method. The estimate made cardiovascular risk assessment feasible in routine practice, without ultracentrifugation.

LDL is usually read together with other markers of metabolic risk, such as the HOMA-IR insulin resistance index and BMI.

How to use the calculator: inputs and results

The calculator asks for the three tests of the lipid panel, all in mg/dL:

• Total cholesterol, between 50 and 1,000. Example: 200.
• HDL cholesterol, between 5 and 200 and lower than total cholesterol. Example: 50.
• Triglycerides, between 10 and 5,000. Example: 150.

Values outside these ranges produce a message saying which field to correct; a calculated LDL equal to or below zero also produces an inconsistent-data warning. With triglycerides below 400 mg/dL, the tool returns:

1. Calculated LDL cholesterol, in mg/dL, with one decimal place.
2. Estimated VLDL cholesterol (triglycerides ÷ 5), in mg/dL.
3. Non-HDL cholesterol (total cholesterol − HDL), in mg/dL.
4. Ratios total cholesterol/HDL, triglycerides/HDL and LDL/HDL, with two decimal places and no interpretation range.

With triglycerides of 400 mg/dL or more, LDL and VLDL are not calculated: only non-HDL and the total cholesterol/HDL ratio appear, with a warning explaining why. A note reminds you that targets depend on cardiovascular risk.

Friedewald formula and worked example

Friedewald LDL is calculated by subtracting HDL and one fifth of the triglycerides from total cholesterol, all in mg/dL. In mmol/L, the triglyceride divisor would become 2.2, but this calculator accepts only mg/dL.

LDL (mg/dL) = Total cholesterol − HDL − (Triglycerides ÷ 5)

In a second case, with total cholesterol 250, HDL 40 and triglycerides 450 mg/dL, the tool calculates neither LDL nor VLDL, warns that the triglycerides exceed the limit and shows a non-HDL of 210.0 mg/dL. Non-HDL does not depend on any estimate and remains useful in this situation.

How to understand LDL: targets by cardiovascular risk

Interpretation of LDL depends on the patient's cardiovascular risk, not on a single normal range. According to a summary by the Brazilian Society of Clinical Analyses (SBAC) of the 2025 guideline of the SBC (Brazilian Society of Cardiology), the targets are:

Stratification considers age, established atherosclerotic disease, diabetes, chronic kidney disease and other factors; therefore, the same LDL of 110 mg/dL may be at target for one person and well above it for another. In kidney disease, the glomerular filtration rate by CKD-EPI enters the stratification. The tool shows the TC/HDL, TG/HDL and LDL/HDL ratios without an interpretation range. The target and the treatment are defined by the attending physician.

Fasting, collection, units and verification checklist

A 12-hour fast has no longer been mandatory for the lipid panel in Brazil since the 2016 Brazilian Consensus for the Standardization of Laboratory Determination of the Lipid Profile. The consensus was signed by SBC, SBPC/ML, SBAC, SBD and SBEM (Brazilian societies of cardiology, clinical pathology, clinical analyses, diabetes and endocrinology). A usual meal, without a fat overload, has little effect on the results.

Points of the consensus that affect calculated LDL:

• Without fasting, the desirable triglyceride level is up to 175 mg/dL.
• With non-fasting triglycerides above 440 mg/dL, the physician considers ordering a new measurement after a 12-hour fast.
• The laboratory must state the metabolic state at collection in the report.

Checklist before using the result:

• Are all three values in mg/dL? To convert from mmol/L, multiply cholesterol by 38.67 and triglycerides by 88.57.
• Are the tests from the same sample?
• Are the triglycerides below 400 mg/dL?
• Did LDL come out below 70 mg/dL with triglycerides between 150 and 399? In that case, the estimate may be too low (see limits).

Patients with diabetes often have high triglycerides; the estimated average glucose from HbA1c helps read metabolic control.

When the Friedewald formula should not be used

The Friedewald formula should not be used with triglycerides above 400 mg/dL, a limit defined by the authors themselves in 1972. The tool is slightly more conservative and does not calculate LDL from 400 mg/dL upward. Above this value, the five-to-one ratio between triglyceride and cholesterol in VLDL no longer holds.

There are other situations in which the result is misleading:

• Low LDL with moderately high triglycerides: Martin and colleagues (JAMA, 2013) showed that the formula underestimates LDL when it is below 70 mg/dL and triglycerides are between 150 and 399 mg/dL. That is precisely the range of people on intensive treatment.
• Presence of chylomicrons, as in samples collected shortly after a fatty meal.
• Dysbetalipoproteinemia (type III), in which VLDL are rich in cholesterol.

In these cases, the laboratory may report LDL by a direct method or by another equation, and non-HDL cholesterol becomes the most reliable parameter. The 2025 Brazilian guideline recommends evaluating non-HDL when triglycerides exceed 800 mg/dL.

Friedewald, Martin/Hopkins, Sampson and direct LDL: which to use

The 2025 Brazilian Guideline on Dyslipidemias and Prevention of Atherosclerosis, from the Brazilian Society of Cardiology, recommends the Martin/Hopkins equation for calculating LDL in all individuals. The table compares the four ways of obtaining LDL.

For the same profile, the difference between methods is usually small with normal triglycerides and grows as they rise. Therefore, when comparing reports from different laboratories, check which method each one used.

Frequently asked questions about LDL calculated by the Friedewald formula

References

1. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;18(6):499-502. View
2. Martin SS, Blaha MJ, Elshazly MB, Toth PP, Kwiterovich PO, Blumenthal RS, et al. Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile. JAMA. 2013;310(19):2061-8. doi:10.1001/jama.2013.280532. View
3. Sampson M, Ling C, Sun Q, Harb R, Ashmaig M, Warnick R, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol. 2020;5(5):540-8. doi:10.1001/jamacardio.2020.0013. View
4. Rached FH, Miname MH, et al. Diretriz Brasileira de Dislipidemias e Prevenção da Aterosclerose – 2025. Arq Bras Cardiol. 2025;122(9). doi:10.36660/abc.20250640. View
5. SBC/DA, SBPC/ML, SBAC, SBD, SBEM. Consenso Brasileiro para a Normatização da Determinação Laboratorial do Perfil Lipídico. 2016. View
6. Sociedade Brasileira de Análises Clínicas. Dislipidemia: as novas metas da Diretriz 2025. View