Which LDL is right?
The LDL on most reports is calculated, not measured. Slide triglycerides up and watch the equations split, then see which one your lab used.
The gap between them: 3 mg/dL.
The 2026 guideline prefers Martin/Hopkins or Sampson/NIH over Friedewald, mostly because Friedewald slips when triglycerides are 150 or more or LDL is under 70.
Friedewald assumes a fifth of your triglyceride number is cholesterol in other particles. In 1.35 million real panels, the middle half ran from 1 in 4.5 to 1 in 6.
How often each one lands in the right class
In over 5 million patients, the share of LDL values each equation put in the right guideline class (bars start at 70%). At an LDL under 70 with triglycerides of 150 to 199, the newer method agreed with a measured LDL 92% of the time, Friedewald 61% (Martin 2013).
What your result means
- The two equations land within a few points: your lab's LDL is fine to use, whichever one it printed.
- They split by 10 points or more: this usually happens with triglycerides of 150 or more or an LDL under 70. Trust your non-HDL more, or ask your lab or doctor for the NIH or Martin/Hopkins equation, or a measured (direct) LDL.
- Triglycerides of 400 or more: Friedewald can't be used. A fasting retest or a direct LDL gives a better number, as the guideline suggests.
Whatever the equation, compare two results from the same lab, so a change in method doesn't look like a change in you.
How it works
Friedewald (1972) takes total minus HDL minus a fifth of triglycerides, and can't be used at triglycerides of 400 or more. The NIH equation (Sampson 2020) works to 800. A third, Martin/Hopkins (2013), takes its divisor from a 180-cell table of triglyceride and non-HDL levels, and Johns Hopkins has made it free for any lab to use.
The guideline prefers Martin/Hopkins or the NIH equation, because they differ most from Friedewald when triglycerides are 150 or more, LDL is under 70 or non-HDL is under 100. A typed LDL within 1 mg/dL of one equation is a fair guess at which one your lab used.
5 sources
- Friedewald WT, Levy RI, Fredrickson DS, Estimation of the concentration of low-density lipoprotein cholesterol in plasma, Clinical Chemistry, 1972pubmed.ncbi.nlm.nih.gov
- Sampson M and others, A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia, JAMA Cardiology, 2020doi.org
- Martin SS and others, Comparison of a novel method vs the Friedewald equation for estimating LDL cholesterol, JAMA, 2013pubmed.ncbi.nlm.nih.gov
- Johns Hopkins Medicine, the Martin/Hopkins equation free to use, via EurekAlerteurekalert.org
- Blumenthal RS, Morris PB, Gaudino M and others, 2026 ACC/AHA guideline on the management of dyslipidemia, JACC, 2026doi.org
