Low cholesterol levels are known as hypolipidemia. Obesity, insulin, and smoking can cause low levels of HDL cholesterol. Low levels of LDL cholesterol may result from thyroid problems or other health issues.

People can also have low levels of low-density lipoprotein (LDL) or “bad” cholesterol. Despite the name, the body needs some LDL cholesterol to function. Very low cholesterol levels may be a sign of an underlying disease.

Some potential causes of low overall or LDL cholesterol include chronic infections, inflammation, and malnourishment.

Read on to learn more about what causes low cholesterol.

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High-density lipoprotein (HDL), or good cholesterol, is beneficial cholesterol. Some common causes of low HDL cholesterol include:

Losing weight and quitting smoking may help bring HDL cholesterol to a satisfactory level.

Less commonly, an underlying medical condition may lower HDL cholesterol:

  • APOA1 deficiency: This rare genetic condition affects the APOA1 gene, which is responsible for encoding a protein that forms HDL cholesterol. People with an APOA1 deficiency cannot make as much HDL cholesterol as others.
  • Tangier disease: This is a type of APOA1 deficiency. It causes low or no HDL and low LDL.
  • Familial combined hyperlipidemia (FCH): This is a fairly common disorder that causes low HDL but very high LDL and triglycerides. Scientists believe it occurs due to changes in multiple genes and environmental factors, such as diet and lifestyle.

Learn more about high HDL cholesterol levels here.

LDL cholesterol is informally known as “bad” cholesterol. Usually, doctors encourage people to lower LDL cholesterol levels. However, when LDL levels fall below 50 milligramsperdeciliter(mg/dL) of blood, this may signal a health problem or cause symptoms.

Low LDL cholesterol is less common than low HDL cholesterol. Typically, it is secondary to another medical condition, such as:

Three genetic disorders may cause low LDL cholesterol:

  • Hypobetalipoproteinemia: A person must inherit two copies of a gene for this condition to develop. It causes the body to metabolize LDL very quickly. Some people with this disorder have no detectable levels of LDL and need treatment. Others have low but detectable LDL levels and do not usually need treatment.
  • Chylomicron retention disease: To develop this condition, a person has to inherit two copies of a certain gene – one from each parent. Symptoms usually present in infancy and can cause nutritional malabsorption, failure to thrive, and fatty stools. It is also known as Anderson’s disease.
  • Abetalipoproteinemia: This condition, also known as Bassen-Kornzweig syndrome, means a person cannot absorb fat from their diet. Babies usually show symptoms and may have a very low weight, intellectual disabilities, and failure to thrive.

Low LDL cholesterol may also occur if a person is taking cholesterol-lowering medication.

Learn more about LDL cholesterol here.

People with low cholesterol will not necessarily have symptoms. When they do, those symptoms may be from the low cholesterol itself or from the underlying disease that is causing low cholesterol.

Some potential symptoms of low cholesterol include:

  • fatty stool
  • depression
  • vision changes
  • hormonal imbalances
  • weight loss or failure to thrive in babies
  • intellectual disabilities or cognitive impairments in children

Learn about the ratio of cholesterol in the body here.

HDL cholesterol protects against the oxidation of LDL cholesterol. People with low HDL cholesterol may have high LDL cholesterol or high total cholesterol. This increases their risk of heart disease.

Low overall cholesterol has different effects. Cholesterol helps the body make vitamin D, steroid hormones, such as cortisol, and sex hormones, such as estrogen and testosterone. Low cholesterol levels may affect the synthesis of these chemicals.

It also helps the body produce the bile necessary for digestion and absorption of vitamins A, K, E, and D and helps form the cell membrane of each cell in the body.

Without cholesterol, many bodily functions may not work as well. This can affect metabolism, nutritional status, and mental and physical health.

Learn more about vitamins and their function here.

Most laboratories determine a person has hypolipidemia if there is less than 120 mg/dL of cholesterol in their blood or less than 50 mg/dL of LDL cholesterol.

Doctors test cholesterol with a lipid panel. This is a blood test that measures concentrations of lipids, including cholesterol, in the blood.

The typical ranges for cholesterol in adults are as follows:

Typical range
Total cholesterol120–150 mg/dL
LDL cholesterol50–100 mg/dL
HDL cholesterolmore than 40 mg/dL in males and 50 mg/dL in females

A doctor may recommend additional tests, such as tests for genetic disorders or infections, to find the underlying cause of low cholesterol.

Learn more about lipid tests here.

Treatment for low cholesterol depends on the type of low cholesterol a person has and what caused it.

Low HDL often gets better with lifestyle changes such as:

  • quitting smoking
  • attaining a moderate weight
  • becoming more physically active

Low LDL cholesterol may require treatment if a person has symptoms or an underlying genetic disorder. Treatment for the genetic disorders that cause low LDL cholesterol may include taking vitamin E supplements and other fat-soluble vitamins. Sometimes, a doctor may recommend supplementing the diet with more fat.

Learn more about LDL cholesterol here.

Some questions to ask a doctor include:

  • Is my cholesterol too low?
  • Does it require treatment?
  • Will any diet or lifestyle changes help?
  • Could my medication be causing low cholesterol?
  • Is low cholesterol responsible for my symptoms?
  • What are the most likely explanations for my low cholesterol?
  • Are there additional tests we can do to find the root cause?

Low HDL cholesterol is relatively common. It may be due to lifestyle or a medical condition. Low LDL or overall cholesterol is less common and may signal an underlying medical condition or a genetic disorder.

The effects of and treatment for low cholesterol depend on its cause. Talk with a doctor about treatment, diagnosis, and management.