Cholesterol has a bit of an image problem. Say the word and most people picture clogged arteries and a doctor reaching for the prescription pad. And it does matter: in New Zealand, around 1 in 9 adults is on medication for high cholesterol (13.4% of men and 9.6% of women).1
Over time, raised cholesterol can contribute to atherosclerosis, where fatty plaque builds up inside the artery walls. That is different from arteriosclerosis, the broader hardening and stiffening of the arteries. Both make it harder for blood to flow the way it should.
But here is the part that often gets left out. Cholesterol is not all bad. It is an essential lipid, and your body cannot function without it.
The case for cholesterol
Cholesterol quietly does a lot of important work:
- Cell walls: it keeps the walls of every cell in your body flexible and stable.
- Bile, vitamin D and hormones: it is the raw material for bile (made by the liver to help digest fats and clear waste), vitamin D, and steroid hormones such as oestrogen, progesterone and cortisol.
- Brain and nerves: it is a key part of myelin, the insulation around your nerves, and supports nerve signalling, memory and brain function.
Cholesterol does not travel around the bloodstream on its own. It is carried inside particles called lipoproteins, and the different types are what a cholesterol test measures. So cholesterol is not something to fear, but as we age it is something worth keeping an eye on. That is why your doctor may order a lipid blood test.
What your cholesterol test is telling you
Plenty of people find the numbers and flags on a cholesterol test confusing. Here is an example of what your results might look like, followed by what each line means.
Patient: J. Sample (fictional) | Age: 52 | Sex: Male | Sample type: Serum | Fasting
| Parameter | Result | Units | Target (adults 19+) | Flag |
|---|---|---|---|---|
| Total cholesterol | 6.1 | mmol/L | <5.0 | High |
| HDL cholesterol | 0.9 | mmol/L | >1.0 | Low |
| LDL cholesterol | 4.0 | mmol/L | <3.4 | High |
| Triglyceride (TG) | 2.4 | mmol/L | <2.0 | High |
| Total/HDL ratio | 6.8 | ratio | <4.5 | High |
| Non-HDL cholesterol | 5.2 | mmol/L | <4.2 | High |
Target limits are the adult reference ranges used by Awanui Labs.2 They are a general guide for adults without major cardiovascular risk factors, not a diagnosis on their own.
HDL: the good one
HDL (high-density lipoprotein) is the one you want plenty of. Think of it as the clean-up crew: it picks up excess cholesterol from your cells and carries it back to the liver to be broken down and removed. Because it clears cholesterol away, a higher HDL is a good thing. It is the one number where a low result, as in our example, gets flagged rather than a high one.
LDL: the one to watch
LDL (low-density lipoprotein) does the opposite job, transporting cholesterol out to the cells. That is necessary, but when too much is circulating, the excess gets deposited in the artery walls. Over time those deposits cause damage, narrowing and blockages. That is the plaque build-up behind atherosclerosis, and it is why LDL is the number most people are told to bring down.
Triglycerides: three fats and a backbone
The name gives it away. Each triglyceride is three fatty acids attached to a glycerol backbone: tri (three) plus glyceride (glycerol).
Triglycerides are your body's way of storing spare energy. Eat more than you need and the extra is tucked away in fat cells, then released between meals to be burned as fuel. High levels are common when calories regularly outpace what you burn, especially from sugar, refined carbs and alcohol. Persistently raised triglycerides are linked to heart disease and often show up alongside low HDL and poor blood sugar balance.
Total cholesterol: the headline number
This is all the cholesterol in your blood added together: HDL, LDL and the cholesterol carried in other particles. It is a useful starting point, but on its own it does not tell you whether the balance is healthy. That is what the next two numbers are for.
Total/HDL ratio: the balance check
This divides your total cholesterol by your HDL, showing how much of your total is made up of the protective kind. A lower ratio is better. The target is under 4.5, so the example result of 6.8 shows that too little of this patient's cholesterol is HDL.
Non-HDL cholesterol: the fuller picture
This is your total cholesterol minus your HDL, so it captures all the cholesterol carried in the particles that can contribute to plaque, including LDL. Definitely one to watch.
The takeaway
Cholesterol is neither hero nor villain. It is an essential part of how your body works, and the goal is not to get rid of it but to keep the different types in balance. If your test comes back with a few flags, treat it as an opportunity to make some lifestyle changes that support healthy ageing, and talk to your GP about what your numbers mean for you.
This is the first article in our cholesterol series. Next, find out why cholesterol is really an inside job, then explore 6 lifestyle changes for healthy cholesterol.
References
- Ministry of Health. New Zealand Health Survey 2024/25: Adults diagnosed with high cholesterol and taking medication. Released 19 November 2025. health.govt.nz
- Lipid target limits sourced from Awanui Labs (effective 6 December 2025).
