Your blood cholesterol levels contribute to your risk of heart disease, heart attack, and stroke. Based on your blood test results, each lab may calculate your “bad” low-density lipoprotein (LDL) differently.

You have several types of cholesterol in your blood — but your low-density lipoprotein (LDL) cholesterol is considered the “bad” cholesterol. High levels of this cholesterol increase your risk of heart disease and related complications.

Laboratory tests can determine your LDL cholesterol through a blood sample. But how exactly do they calculate this number?

Keep reading to find out about LDL cholesterol, how laboratories calculate this value, and steps you can take to keep your LDL cholesterol numbers low.

When you receive a report of your blood test for LDL cholesterol, you’ll see an amount measured in milligrams per deciliter of blood. While you should look at the normal values that the laboratory lists, your optimal LDL cholesterol level should be around 100 mg/dL or less.

Your LDL cholesterol is also a component of your total cholesterol — according to the Centers for Disease Control and Prevention (CDC), this number should be around 150 mg/dL.

Your LDL numbers may vary from lab to lab because each lab may use a different calculation. Some studies have detailed as many as 11 potential calculations that labs can use to calculate LDL cholesterol.

The Friedewald equation

The Friedewald equation is a commonly used equation for calculating LDL cholesterol:

LDL Cholesterol = (Total Cholesterol) − (HDL Cholesterol) − (Triglycerides/5)

Some experts question the accuracy of using the triglycerides calculation, saying the calculation could cause a person’s LDL cholesterol to seem too low.

Martin/Martin-Hopkins equation

There’s a newer equation called the Martin or Martin-Hopkins equation. This calculation eliminates the triglycerides/5 value and replaces it with a variable number that depends on your triglyceride and non-high-density lipoprotein (HDL) levels.

A 2020 article in JAMA Cardiology on LDL calculations found the Martin equation to be more accurate than the Friedewald equation.

And in 2018, the American College of Cardiology and the American Heart Association recommended that laboratories use the Martin equation for calculating samples with low LDL cholesterol levels.

National Institutes of Health (NIH) and LDL cholesterol equation

LabCorp, one of the largest laboratory organizations in the United States, uses the National Institutes of Health (NIH)‘s calculation for the LDL:

LDL Cholesterol = Total Cholesterol/0.948 − HDL Cholesterol/0.971 − (Triglycerides/8.56 + Triglycerides × Non-HDL Cholesterol/2,140 − Triglycerides2/16,100⁠) – 9.44

Their laboratory previously used the Friedewald equation.

The Friedewald equation was previously used more widely, but newer equations have potentially helped to enhance the accuracy of LDL calculations on blood tests.

The accuracy of calculated LDL on a lab blood test can also depend on a number of factors:

  • Calculated LDL can be dependent on you being in a fasting state before taking your test. If you take your cholesterol test when a doctor or healthcare professional directs you to fast and you don’t, the Friedewald equation is especially likely to be inaccurate.
  • The accuracy of calculating LDL cholesterol often depends on the results of your other cholesterol numbers, including your triglycerides and HDL levels. Very high or low levels of these numbers can affect the accuracy of all types of clinical calculations.
  • If you have very high triglyceride levels (higher than 400 mg/dL), a doctor or measuring laboratory may recommend using a direct LDL cholesterol test. This test is likely more expensive but more accurate.

You can also contact the laboratory that performed your testing or talk with a doctor about the potential accuracy or factors that may influence how accurate your LDL calculations are.

LDL and your overall health

Keep in mind that a doctor won’t only look at your LDL calculation when determining how to treat your cholesterol readings. They’ll also consider:

  • your cholesterol reading history
  • family history of cholesterol levels
  • other chronic health conditions you may have

For example, if you have high cholesterol levels along with other risk factors for heart disease, such as high blood pressure or diabetes, a doctor may recommend medical treatment. But if you have few other risk factors, they may recommend starting with lifestyle changes before any additional medical or surgical treatment.

Lowering LDL cholesterol levels often takes a combination of diet and lifestyle changes as well as taking medications to lower your levels.


Dietary fat sources contain cholesterol. Traditionally, this means that reducing fat intake has been recommended to lower cholesterol. But researchers have found that lowering cholesterol isn’t just about reducing fat intake overall, but focusing on what types of fats you eat.

Eating trans fats found in a lot of shelf-stable foods, such as prepackaged sweets, can increase your risk of cardiovascular disease. Replacing high levels of saturated fats (often found in high-fat cuts of meat) with unsaturated fats and higher-fiber carbohydrates can also help.

With this in mind, here are some healthy choices you can make to help lower your cholesterol:

  • Eat lean cuts of meat whenever possible: This includes skinless chicken and low-fat beef cuts.
  • Read food labels carefully: Avoid eating foods with trans fats whenever possible.
  • Choose high-fiber carbohydrates:Eat high-fiber foods when possible to complement lean meat choices.
  • Choose unsaturated fats over saturated fats when possible:Unsaturated fats include avocados, nuts, seeds, and olive, peanut, and canola oils.
  • Incorporate sources of omega-3 fatty acids in your diet: Examples include fish, flax seeds, walnuts, and canola or soybean oil.

Remember that you shouldn’t sacrifice eating fats for eating carbohydrates that have little to no nutritional value, such as replacing eating a steak with French fries. These food swaps can actually increase your cholesterol.


Lifestyle changes that can help lower cholesterol include:

  • stopping smoking if you smoke
  • engaging in regular physical activity (30 to 60 minutes most days of the week) to keep up a moderate weight
  • managing your chronic health conditions, such as controlling diabetes

You can also ask a doctor about specific lifestyle changes that may benefit your overall health.


The CDC estimates that only a little more than half (54.5%) of people who can benefit from taking cholesterol-lowering medications actually take them.

But several types of cholesterol-lowering medications exist that can help lower and control LDL cholesterol, including:

  • Statins:Statins are some of the most commonly prescribed medications to treat high cholesterol. These medications help reduce how fast your liver produces cholesterol and lower your overall cholesterol levels.
  • Bile acid sequestrants:These medications help remove bile acids and help to lower cholesterol.
  • Injectables:Injectable medications are newer to the cholesterol-lowering market. Doctors typically prescribe these medications to those who have familial hypercholesterolemia, a disorder that causes very high LDL levels.
  • Niacin: This B vitamin can help increase HDL, or “good,” cholesterol levels while lowering LDL and total cholesterol. But niacin can have some uncomfortable side effects such as facial flushing, so it’s not the right treatment for everyone.

If you’ve received a diagnosis of high cholesterol, ask a doctor if cholesterol-lowering medications could benefit you. Be sure to discuss side effects and what benefits you can realistically expect as well.

If you haven’t had your cholesterol checked in some time (or ever), talk with a doctor about getting this blood test — especially if you have a family history of high cholesterol or heart disease.

Tracking your cholesterol levels over time can help you establish if you’re at risk of cardiovascular disease. Lifestyle changes and medications can help you keep your LDL cholesterol levels at a healthy range.