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LDL is also known as ‘bad’ cholesterol and measuring your levels can give you a good insight into your risk of developing heart disease.

Author: Leanne Edermaniger

April 19, 2024

Reviewed by: Dr Thom Phillips

In this article:

What is Low-density Lipoprotein (LDL)?

Low-density lipoprotein (LDL), sometimes referred to as LDL cholesterol, is a type of fat that circulates in the bloodstream transporting cholesterol around the body. LDL is commonly known as bad cholesterol because it deposits excess cholesterol on the artery walls.

The excess can form plaques which cause your blood vessels to narrow making it more difficult for blood to travel to your vital organs. If the vessels become too blocked and blood flow is severely restricted or some of the plaque breaks away and causes a blockage elsewhere, it increases the risk of cardiovascular problems such as angina, heart attacks, and strokes[1].

High-density lipoprotein (HDL) cholesterol, however, is known as ‘good’ cholesterol because it returns cholesterol back to the liver where it can be processed and removed from the body.

What Should LDL Levels Be?

Ideally, LDL cholesterol should be below 3.0 mmol/L to be within a healthy range[2]. Our data shows that 48% of Forth customers have high LDL levels which can be broken down by age:

Age Average LDL level (mmol/L) % of Forth Customers with a High LDL Level
18-29 2.6 26.6%
30-39 2.9 42.5%
40-49 3.1 50,3%
50-59 3.4 66.1%
60+ 3.4 61.6%

Research shows that LDL:HDL ratio is likely to be a better predictor of atherosclerosis and heart disease compared to LDL measurements alone[3]. Previous studies have shown that a high LDL to HDL ratio is associated with cardiovascular events, such as heart attacks[4]. It’s also called non-HDL cholesterol and is effectively your total cholesterol minus your ‘good’ or HDL cholesterol, giving you a total figure of the bad cholesterol in the blood, including LDL. Ideally, this figure should be as low as possible.

According to the British Heart Foundation, one in fourteen women die from coronary heart disease (CHD) in the UK per year. It may also surprise you to learn that CHD kills more than twice as many women in the UK as breast cancer so it’s a big problem.

Unfortunately, often the first symptom of CHD is a heart attack, at which point it’s a little late! Research has suggested that the changes in hormones that happen during menopause can affect the way cholesterol is processed, increasing your risk closer to that of a man of a similar age.

Oestrogen, known for its cardioprotective effects, declines during menopause, leading to increases in total cholesterol levels, and specifically, an increase in low-density lipoprotein cholesterol (LDL-C)
Although we often think about Hormone replacement therapy (HRT) to alleviate the classic menopausal symptoms it is also important to consider that the extra oestrogen may potentially mitigate these adverse changes in lipid metabolism. This is something you should discuss with your GP.

What Causes High and Low LDL Levels?

The risk of high cholesterol increases with age. Total cholesterol levels steadily rise between the ages of 20 and 65, before plateauing for women and falling slightly in men[5].

There are several other risk factors for high levels of circulating LDL, including a family history. For example, familial hypercholesterolaemia is a genetic disease where the body struggles to clear LDL cholesterol from the body, increasing the risk of early heart disease[6]. Because it is genetic, it is passed down through families with approximately 1 in 250 people affected.

People who are living with metabolic diseases such as obesity or type 2 diabetes are also at a greater risk of developing high levels of bad cholesterol. One study has shown that 62% of people with type 2 diabetes were at a high risk of increased LDL cholesterol levels[7].

Unhealthy behaviours or lifestyle choices also increase the risk of high blood LDL levels, including:

  • Smoking increases fat levels, such as LDL and triglycerides, in the blood raising the risk of heart disease[8].
  • Although moderate alcohol intake may have some protective benefits, excessive alcohol consumption, more than 30 g/day, is associated with an increase in total cholesterol and triglyceride levels[9].
  • Not getting enough physical exercise affects blood lipid levels. That’s because exercising regularly is known to promote ‘good’ or HDL cholesterol while maintaining LDL and triglyceride levels. Intense exercise can even reduce these levels[10].

There are several other risk factors for high LDL cholesterol. They are:

  • Age. Cholesterol levels naturally increase with age.
  • Certain medications. Some medicines can interfere with your cholesterol levels, like beta-blockers, chemotherapy, diuretics, arrhythmia medicines, and steroids.
  • Underlying medical conditions. Diabetes, obesity, polycystic ovary syndrome (PCOS), hypothyroidism, and chronic kidney disease can alter your cholesterol levels.
  • Race or ethnicity. Non-white Hispanic people are most at risk of high LDL levels.
  • Sex. Men are more likely to have high cholesterol between the ages of 20 and 39,the risk for women increases after menopause.

Symptoms of High LDL

High cholesterol doesn’t often present with any symptoms, so it is possible to be walking around with high LDL and not know anything about it. That’s why it is called a ‘silent killer’. For this reason, it is important to monitor your levels with a cholesterol test, to measure your cardiovascular risk.

If you have an inherited condition that causes high LDL levels, then you may have some noticeable signs, such as:

  • Swellings around your knuckles, knees or Achilles’ tendons
  • Small yellow lumps of cholesterol around the inner corner of your eye
  • A pale white ring around the coloured part of your eye, the iris

Low LDL Levels

Low LDL levels can be caused by genetics or acquired or environmental factors.

The most common genetic cause of low LDL levels is an inherited condition called heterozygous familial hypobetalipoproteinaemia. It means that the body can’t properly absorb and transport fats[11].

Symptoms of Low LDL

Some of the symptoms associated with low LDL levels may include:

  • Failure to thrive with diarrhoea
  • Fatty poo because the body is unable to absorb fat properly
  • Ataxia (a condition that affects co-ordination, balance, and speech)
  • Pigmentation of the retina
  • Build-up of fats in the liver[12]

How to Improve Your LDL Levels

Fortunately, there are things you can do to proactively help lower or improve your LDL cholesterol levels. They include:

  • Following a healthy balanced diet which limits your intake of saturated fat and sugar
  • Aiming to exercise for at least 30 minutes daily for at least five days per week
  • Quitting smoking if you are a tobacco smoker
  • Trying to limit your alcohol intake to no more than 14 units per week, spread across at least three days

If a medical professional is concerned about your LDL levels they may prescribe medication which can help bring it down, like statins.

How to Test Your LDL Levels at Home

Testing your LDL levels at home is simple with a range of at-home blood tests from Forth.

We offer the following tests which measure LDL cholesterol levels:

Cholesterol Blood Test. Measuring five key biomarkers for heart health, this test will give you an accurate view of your lipid profile, including LDL, HDL, total cholesterol, HDL ratio, and triglycerides.

Baseline Health Check. This test measures 25 biomarkers to give you a snapshot into your overall health and wellbeing, including heart health, bone health, liver function, and energy levels.

Ultimate Health Check. For a more comprehensive view of your health, this test includes 47 biomarkers to analyse your heart health, thyroid function, immunity, hormones, and much more.

Nutricheck – Vitamin Deficiency Blood Test. Use this test to find out how your diet is contributing to your overall health and wellbeing.

What Other Biomarkers Should I Test Alongside LDL?

As well as measuring total cholesterol, HDL, HDL ratio, and triglycerides alongside LDL, we also recommend:

  • hs-CRP. This biomarker is a good indicator of low-grade inflammation in the body. It is also a good biomarker for heart health because it is released by smooth muscle cells in atherosclerotic arteries, the type where LDL-cholesterol has been deposited[13].
  • Thyroid stimulating hormone (TSH) and Thyroxine. These biomarkers can give you an insight into your thyroid function, a small butterfly-shaped gland in the neck responsible for regulating metabolism. People with an underactive thyroid, hypothyroidism, often have increased LDL cholesterol levels, as the body is unable to clear the bad cholesterol appropriately. So, testing your thyroid health can indicate if high cholesterol is being caused by thyroid dysfunction.
  • HbA1c. A HbA1c test provides an average glucose reading over a three-month period and is a good indicator of pre-diabetes. Type 2 diabetes increases the risk of high cholesterol levels. A HbA1c test may help to identify if diabetes is a contributing factor to high LDL levels.

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

- Health scores calculated


Article references

  1. Mohamed, E., Mohamed, M., & Rashid, F. A. (2004). Dyslipidaemic pattern of patients with type 2 diabetes mellitus. The Malaysian journal of medical sciences : MJMS, 11(1), 44–51.

  2. Tsimikas, S., Willerson, J.T. and Ridker, P.M. (2006) ‘C-reactive protein and other emerging blood biomarkers to optimize risk stratification of vulnerable patients’, Journal of the American College of Cardiology, 47(8). doi:10.1016/j.jacc.2005.10.066.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services