Dangerous Cholesterol Levels, Types, Dangers and Risks

Cholersterol is a type of fat that is needed for various functions in the body. Not only is some cholesterol sourced in food but the body also produces cholesterol. It is fair to say that cholesterol is essential for health and life but it can also be dangerous when present in high levels within the body.

Excessive cholesterol and other types of fatty acids are one of the main factors in coronary artery disease, which is now one of the leading causes of heart disease. It is therefore important to understand when cholesterol levels are too high and even dangerous to one’s life.

Cholesterol in the Body

There are two sources of cholesterol in the body.

  • Endogenous cholesterol is produced in the body and mainly in the liver.
  • Exogenous cholesterol is sourced from food in the gut.

Cholesterol is transported in the bloodstream bound to proteins. The two main types of protein-bound cholesterol that is important to monitor is LDL-C (low density lipoprotein cholesterol) and HDL-C (high density lipoprotein cholesterol). LDL-C is also referred to as “bad cholesterol” while HDL-C is known as the “good cholesterol”.

Read more on what is cholesterol.

Blood Cholesterol Levels

The most common test that is done is the total cholesterol blood test. The test is done by taking a fasting blood sample in the morning. No food should have been consumed at least 8 hours prior to taking the blood sample. It is important but does not indicate the entire situation about cholesterol in the body. These are the meanings of blood cholesterol readings:

  • NORMAL = Less than 5.2 mmol/L or 200 mg/dL
  • BORDERLINE HIGH = 5.2 6.2 mmol/L or 200 239 mg/dL
  • HIGH = Above 6.2 mmol/L or 240 mg/dL and above

The LDL-C and HDL-C levels are also important considerations, as well as the LDL-C to HDL-C ratio. Triglycerides is another type of lipid that may also be considered in a lipid profile (lipogram). Although LDL-C is considered to be the more “dangerous” type of cholesterol, it has to be also be viewed in the backdrop of the HDL-C levels.

When are cholesterol levels dangerously high?

Any blood cholesterol level, known as hypercholesterolemia, within the high range (above 6.2 mmol/L or 240 mg/dL and above) should be considered dangerous. It is well know that the higher levels are associated with a high risk of atherosclerosis. This is where fatty plaques form in the walls of the arteries. These plaques can rupture and if this occurs then a blood clot can form within the affected vessel.

Ultimately blood flow through these narrowed arteries is reduced. Therefore the target organ receive less oxygen and nutrients. The greater risk lies when the arteries to vital organs like the heart or brain are narrowed by these fatty plaques. Other factors like high blood pressure (hypertension) also compound the high blood cholesterol levels thereby causing it to be a more serious and even dangerous situation.

Read more on HDL and LDL Cholesterol Tests.

Dangers and Risks of High Cholesterol

The main danger associated with high cholesterol is atherosclerosis. This can affect any artery of any organ but it is most dangerous when the arteries supplying the vital organs are affected. The heart and brain are at greatest risk. When these organs stop functioning for even just a few minutes then death can occur.

The heart and brain are commonly affected sites in atherosclerosis. Another commonly affected site is the leg arteries. This is known as peripheral arterial disease. However, the disturbance in the leg arteries are usually not considered dangerous although it may be serious.


The coronary arteries are the main arteries to supply blood to the muscular heart wall. These arteries are prone to atherosclerosis.  This means that fatty plaques composed of cholesterol, other lipids and blood cells form in the wall of the atery. These plaques cause the coronary arteries to become narrowed and this is known as coronary artery disease (CAD). It is one of the main consequences and most serious complications of high cholesterol levels.

These plaques may not cause any symptoms despite the arteries being narrowed. Sufficient oxuygen-rich blood may still be able to flow through it under normal circumstances. However, when the heart is working harder and needs more oxygen-rich blood then the narrowed arteries may not be able to cope. Insufficient blood reaches the heart an this can cause heart muscle injury known as ischemia. It may cause chest pain which is known as angina pectoris.

The heart is slowly starved of oxygen which is referred to as ischemic heart disease. Sometimes these fatty plaques rupture and a blood clot forms. The already narrowed artery is then almost completely blocked by the blood clot. Little to no bloo reaches the heart muscle and this can cause tissue death. This sudden death of a portion of the heart muscle is known as a heart attack (myocardial infarction).


The brain receives blood through several branches of the carotid and vertebral arteries. These arteries can also become narrowed due to atherosclerosis. Elevated blood cholesterol levels are only one factor that contributes to atherosclerosis. High blood pressure (hypertension), diabetes and other factors also contribute to the development of these fatty plaques.

A clot can form in the narrowed artery thereby blocking off the blood flow. However, more commonly the blockage is from a blood clot that forms elsewhere in the circulatory system. This clot may then break away from where it formed (emolus), travel through the bloodstream and eventually lodge in the narrowed part of an artery supplying the brain. A portion of the brain tissue may then die due to insufficient oxygen and this is known as a stroke.

Most strokes (cerebrovascular accident) are due to clots which blocks the blood supply and are referred to as ischemic strokes. Sometimes the narrowed artery is not fully blocked but the blood flow through it is insufficient for the brain’s needs. This can cause episodes of stroke-like symptoms which are temporary. These episodes are known as transient ischemic attacks (TIAs). Death of brain tissue does not occur in TIAs as occurs in strokes.

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