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Cholesterol: Definition, Normal & High Levels + How to Lower

Written by Biljana Novkovic, PhD | Last updated:
Ognjen Milicevic
Puya Yazdi
Medically reviewed by
Ognjen Milicevic, MD, PhD, Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

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Cholesterol plays a key role in the body – it helps produce hormones and balances nutrients. But too much cholesterol can block arteries, lead to heart disease and an array of other problems. Read on to learn about healthy cholesterol levels and which lifestyle and dietary changes can help you lower them.

What Is Cholesterol?

Cholesterol is a type of lipids (sterol) used to build cell membranes, hormones, and vitamin D. You get cholesterol from different animal-based foods such as eggs, meat, butter, and whole-milk dairy products. This fat is often seen as the “bad guy” since many people worldwide struggle with high blood cholesterol levels. But low cholesterol can be equally problematic, although much less common.

Cholesterol is extremely important for your body. In fact, humans have over 100 genes that affect cholesterol production, movement, and breakdown [1, 2].

Properly balanced cholesterol levels are vital for dietary nutrient absorption, hormone levels, reproductive health, fluid and salt balance, as well as for your calcium status. In the adrenal cortex, cholesterol is broken down into pregnenolone, which is used to make all sex hormones [1, 2].

What’s more, cholesterol helps cells communicate and transfers various important molecules into or out of cells. No cell in your body could do without it [1].

Most cholesterol is created in the liver and gut, while smaller amounts are made in other organs [3].

The starting point for producing it in the body is lanosterol. On average, humans make 10 mg/day of cholesterol per kg of body weight – but this is highly individual and depends on many factors. If you eat foods high in cholesterol, less needs to be made in the body [1, 3].

Most people associate cholesterol only with negative health consequences. And it’s true that although a certain amount of cholesterol is vital for your health, high levels can be very dangerous.

High cholesterol is a common problem mostly due to an unhealthy diet or lifestyle, although genetic factors can also play a large role. High cholesterol can increase your risk of heart disease by clogging the arteries [1].

Importantly, it’s not just a matter of whether you have high cholesterol in general. Not all cholesterol is created the same, LDL being the more dangerous or “bad” type. HDL, on the other hand, is usually protective. Their ratio can be much more important than total cholesterol levels.

Measuring Cholesterol

Total cholesterol is measured in what’s called a lipid panel. The panel usually looks at 4 parameters (markers) [4]:

Every person over the age of 45 should get a lipid panel. People under the age of 45, but with a family history of heart disease, diabetes, or chronic kidney disease, should be tested earlier [5].

If you are at a higher risk of heart disease your doctor will probably want to keep track of more than just these markers (check tests such as ApoB, Lp(a), and LDL particles). But for most, a routine lipid panel is a great place to start taking care of your heart health!


Cholesterol that’s found in the blood is bound into particles called lipoproteins. You can think of lipoproteins as the vehicles and cholesterol as the passenger. These lipoproteins differ in density (vehicle size), based on which there are three main types of cholesterol:

  • HDL-cholesterol (high-density lipoprotein cholesterol), known as the “good” cholesterol
  • LDL-cholesterol (low-density lipoprotein cholesterol), known as the “bad” cholesterol
  • VLDL-cholesterol (very-low-density lipoprotein cholesterol), also “bad” cholesterol

Total cholesterol is the sum of these three types of cholesterol in the body. A change in any of these cholesterols will affect total cholesterol score.

Overall, LDL and HDL work together to maintain cholesterol levels. LDL delivers cholesterol from the liver to organs that use it. HDL gathers unused cholesterol from organs and returns it to the liver (and adrenal glands) for reuse or disposal [6].

HDL-cholesterol is known as “good” cholesterol, because HDL particles carry cholesterol away for disposal. LDL-cholesterol, on the other hand, is considered “bad” cholesterol because LDL particles deposit it in tissues such as the arteries. In addition, the less-talked-about VLDL-C can break down to LDL-C, which can clog the arteries [7, 8, 9].

Normal Range

Total Cholesterol

The normal range for total cholesterol is between 100 and 200 mg/dL [10, 11].


Based on the National Cholesterol Education Program (NCEP), LDL-cholesterol levels are classified as:

  • Optimal: < 100 mg/dL (2.59 mmol/L)
  • Near optimal: 100-129 mg/dL (2.59-3.37 mmol/L)
  • Borderline high: 130-159 mg/dL (3.37-4.12 mmol/L)
  • High: 160-189 mg/dL (4.15-4.90 mmol/L)
  • Very high: > 189 mg/dL (4.90 mmol/L)

Read more about LDL-C here.


HDL-C levels can be classified as follows [12, 10]:

  • High risk: < 40 mg/dL (1.0 mmol/L) for men or < 50 mg/dL (1.3 mmol/L) for women
  • Average risk: 40-50 mg/dL (1.0-1.3 mmol/L) for men and between 50-59 mg/dl (1.3-1.5 mmol/L) for women
  • Low risk: > 60 mg/dL (1.55 mmol/L)

Read more about HDL-C here.

High Cholesterol

Slightly and temporarily increased cholesterol is usually not a problem. Consistently increased cholesterol levels, on the other hand, can be dangerous.

Levels above > 240 mg/dL are considered very high [1, 13].

Causes shown below are commonly associated with high cholesterol. Work with your doctor or another health care professional to get an accurate diagnosis. Your doctor will interpret your results, taking into account your medical history, symptoms, and other test results.

What Increases Cholesterol?

Diets High in Calories and Fats

Diet is perhaps the biggest and most significant contributor to elevated cholesterol for most people. One’s diet plays a crucial role in balancing cholesterol. High levels of saturated fat can increase blood cholesterol levels dramatically. This increase is worsened by obesity [1].

The body has many protective mechanisms to stop drastic increases in cholesterol. The health risks due to high cholesterol levels take many years to develop and are a result of eating high-fat foods consistently [1].

The main sources of cholesterol come from eggs, dairy products, and meat. It is estimated that 24.6% of the total cholesterol intake in the U.S. diet comes from eggs. Chicken and beef make up 12.5% and 11%, respectively [14].

Whether cholesterol from the diet can cause heart disease is still unclear. According to a large meta-analysis (of 40 studies and 362k patients), it may not. In the U.S., it’s still not recommended to consume more than 300 mg/day of cholesterol [15, 16].

In other countries such as Australia, Canada, Korea, and India, there are no restrictions on cholesterol, but only on saturated and trans fat, which is likely much more dangerous [15, 16].


Cholesterol levels tend to be higher in those who are overweight and obese [17].

Lack of Exercise

Studies have found an association between lack of physical activity and higher total cholesterol levels, and “bad” cholesterol in particular [18].


Alcohol consumption can increase total cholesterol levels, mainly by increasing HDL cholesterol [19].

Underactive Thyroid

An underactive thyroid gland (hypothyroidism) can also increase cholesterol levels [10, 20].

Thyroid function controls diverse aspects of our metabolism. Even within the normal range of thyroid-stimulating hormone (TSH) values, studies have found a linear increase in total cholesterol, LDL-C and triglycerides with increasing TSH [20].


Many drugs can increase cholesterol levels, including [21, 22]:

  • Corticosteroids
  • Water pills (diuretics)
  • Beta-blockers
  • Antipsychotics
  • Anticonvulsants
  • Anabolic steroids


Familial hypercholesterolemia is a heritable disease that is caused by mutations in several genes, including those that make [23]:

It causes problems in clearing LDL [23].

Some people have reduced activity of genes that break down cholesterol (ABC transporters). This can increase cholesterol levels and a lower response to cholesterol medication [24].

Additionally, your Apolipoprotein E (APOE) variants can have a large impact on your cholesterol and triglyceride levels, aside from affecting your Alzheimer’s risk. APOE helps transport fats in the blood. A well-functioning APOE lowers cholesterol levels, reduces heart disease risk, supports brain health, and decreases excessive inflammation.

How to Lower Cholesterol

The most important thing is to work with your doctor to find out what’s causing your high cholesterol and to treat any underlying conditions.

If your cholesterol levels are high and you are at increased risk of heart disease, your doctor may prescribe drugs such as statins. Statins decrease the amount of cholesterol the liver makes, increase LDL uptake in the liver, and raise HDL cholesterol [25, 26].

Discuss the additional lifestyle changes below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!


Eat a healthy, balanced diet low in saturated fats and processed carbs [27, 28, 29]. Remember, there is no one-diet-fits-all. You’ll need to experiment with healthy diets, track your labs and responses, and consult your doctor (especially if you’re on prescription medication).

Mediterranean Diet

Mediterranean diet is a good example of a healthy diet rich in monounsaturated fats. It includes lots of fruits and vegetables, fatty fish, olive oil, and nuts. Studies have found that it helps lower cholesterol and decrease the risk of heart disease [30, 31, 32, 33].


DASH diet is another type of diet that can help decrease cholesterol levels [34, 35]. This diet is used to lower blood pressure. DASH is, similarly to the Mediterranean diet, rich in vegetables, fruits, lean meats, nuts, and beans. It’s high in fiber and low in fat.

Step 2 diet

The American Heart Association Step 2 diet, which consists of increasing fish, vegetable, fruit, and low-fat dairy products while decreasing salt and alcohol intake, lowers total cholesterol. This diet also reduces LDL by up to 20% [36, 37, 38].

Plant Sterols

Eat more foods high in plant sterols (a type of cholesterol made by plants) including nuts, seeds, and legumes. Plant sterols compete with cholesterol for absorption in the gut, which lowers cholesterol levels [39, 40, 41, 42].


Weight Loss

If you are overweight, losing weight can help lower your total cholesterol [17, 27].

In a study (DB-RCT) of 384 people, weight loss caused total cholesterol levels to decrease by 25 to 30 mg/dL [43].

Regular Exercise

Exercise regularly. Find an activity you enjoy that you can engage in regularly (several times a week), such as jogging, walking, swimming, or resistance training [36, 27].

A meta-analysis of 51 studies and 4,700 adults found that aerobic exercises such as jogging, running, and biking increased HDL by 4.6% and decreased LDL by 5% [44].

Quit Smoking

A study comparing women smokers and non-smokers found that smokers had greater total cholesterol levels (197 mg/dL vs. 189.1 mg/dL) and had lower HDL levels (45 mg/dL vs. 52.1 mg/dL) [45].

Limit Alcohol and Coffee

Don’t exaggerate with alcohol. Alcohol can increase HDL and total cholesterol levels [19]. Although increasing HDL is generally perceived as beneficial, overindulging in alcohol has many negative health effects. Discuss your alcohol consumption with your doctor.

One study suggests that drinking coffee daily may slightly increase cholesterol levels [46]. Try replacing some of your coffee with green tea.


Discuss the following foods and supplements with your doctor. Research has shown they may help decrease cholesterol levels:

Remember, always speak to your doctor before taking any supplements, because they may interfere with your health condition or your treatment/medications!

Low Cholesterol

Low cholesterol levels can signal an underlying health issue.

Causes shown below are commonly associated with low cholesterol levels. Work with your doctor or another health care professional to get an accurate diagnosis. Your doctor will interpret your results, taking into account your medical history, symptoms, and other test results.

These can decrease cholesterol:

  • Serious illness, injury, or surgery – levels gradually increase back up during recovery [94, 95].
  • Bacterial, viral, or parasitic infections [94, 96]
  • Malnourishment (low-protein diets) [97]
  • Malabsorption, in conditions such as celiac disease [98]
  • Anemia (iron deficiency) [99]
  • Overactive thyroid (hyperthyroidism) [20]
  • Liver disease [100, 101]
  • Cancer [94, 102]
  • Rare genetic disorders [103, 104]
  • Statins, drugs used to decrease cholesterol, can in rare cases decrease cholesterol levels below normal [105, 106].

If your cholesterol is below normal, the most important thing is to work with your doctor to find out what’s causing it and to treat any underlying conditions.

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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