What is cholesterol? Understanding LDL, HDL and your blood test results
- chandy Rodgers
- 7 hours ago
- 4 min read
Confused by your cholesterol blood test results? We explain what LDL and HDL cholesterol do and why balance matters more than the numbers.
If you’ve recently had a blood test at your GP surgery, you may be wondering what your cholesterol results mean—or whether cholesterol is actually bad for your health. It is often portrayed as something harmful that must be lowered at all costs, yet it plays several essential roles in the body.
To really understand your cholesterol levels and what they mean for your heart health, it helps to look beyond the simple “good vs bad cholesterol” labels and picture your bloodstream as a busy transport network, carrying vital substances to where they are needed.
In this article, we answer:
What is cholesterol and why is it important for my health?
What is the difference between LDL and HDL cholesterol?
When do cholesterol levels become a problem?
What is cholesterol and why is it important for your health?
High cholesterol, low cholesterol, cholesterol-lowering foods, cholesterol and heart health, cholesterol-lowering drugs—it is a constant topic of conversation, but what exactly is it, and is it all bad?
Cholesterol is a waxy, fat-like substance found throughout your body. Around 70–80% is produced by your liver and other cells (endogenous), while the remaining 20–30% comes from foods (exogenous), such as meat, eggs and dairy.
Why does the body make cholesterol?
Your liver produces the vast majority of your cholesterol because it is a vital building block. Without it, we could not survive. It is the primary raw material for:
Cellular strength: It provides structural integrity for every cell membrane in your body.
Hormonal balance: Cholesterol is the foundation from which steroid hormones are made, including cortisol, oestrogen and testosterone.
Digestion and gut health: It is required to produce bile acids, which allow you to break down and absorb fats.
Vitamin D synthesis: It is essential for producing Vitamin D when your skin is exposed to sunlight.
Put simply, cholesterol is not just rubbish floating in the blood—it is an essential substance being actively transported around the body.
What is the difference between LDL and HDL cholesterol?
Understanding the transport analogy
Because cholesterol is a lipid (a fat), it cannot travel through the blood on its own—much like oil cannot mix with water. To move around the body, it must be carried by proteins called lipoproteins. Think of these as the delivery vans and recycling lorries of your body’s internal transport network.
The two lipoproteins most people are familiar with are LDL cholesterol (low-density lipoprotein), often called “bad” cholesterol, and HDL cholesterol (high-density lipoprotein), often called “good” cholesterol. So what is the difference?
Why is LDL called “bad” cholesterol?
LDL is frequently labelled “bad” cholesterol, but in reality it is simply a delivery vehicle. Its job is to carry cholesterol from the liver out to the tissues and cells that need it—perhaps to repair a cell wall or to produce a hormone.
LDL is not inherently harmful; it is a vital courier service. Problems tend to arise when there are too many vehicles on the road with nowhere to go, or when the vehicles themselves become damaged (oxidised) and begin to cause congestion along the arterial walls.
Why is HDL described as "good" cholesterol?
HDL acts as the body’s internal maintenance and recycling team. Its role—known as reverse transport—is to collect unused or excess cholesterol from the tissues and carry it back to the liver to be repurposed or safely cleared from the system. A healthy HDL level suggests your “clearance” system is working efficiently.
When do cholesterol levels become a problem?
A healthy cardiovascular system is not about eliminating these transport vehicles—it is about balance and flow. From a clinical perspective, problems tend to arise when there is “congestion” in the system. This typically happens when:
There is an oversupply of delivery vehicles (high LDL cholesterol)
The maintenance crew is understaffed (low HDL cholesterol)
The “roads”—your artery walls—are irritated or inflamed, causing transport to get stuck
This is why it is important to look beyond total cholesterol and to consider the LDL/HDL ratio alongside the wider context of your overall health. Is the “traffic” moving smoothly, or is the environment itself creating the problem?
What comes next?
Understanding the transport system is the first step towards a calmer, more informed relationship with your blood test results. In our upcoming posts, we will take a closer look at:
How to read your cholesterol blood test results—what the numbers actually mean
When do cholesterol levels become a health risk?—looking beyond total cholesterol
How can I support my cholesterol health naturally?—foods and lifestyle habits that help keep the roads clear
Want to learn more about fats and how to eat the right things? Sign up to our monthly newsletter and keep an eye out for when we release our online fats course!
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