Cholesterol: What Those Numbers on Your Blood Test Actually Mean

We've all heard the terms "good" cholesterol and "bad" cholesterol thrown around — but what actually is cholesterol, why does your body need it, and what should you really be thinking about when those numbers come back from a blood test?

Let's break it down.

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So, what is cholesterol?

Cholesterol is a waxy, fat-like substance that's an essential building block of every cell in your body. It plays a starring role in producing steroid (sex) hormones, vitamin D, and bile, which helps you digest food.

Your brain holds the highest concentration of cholesterol in the body — around 25% of your total supply.

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How does cholesterol get around your body?

Cholesterol is a fat, and fats don't dissolve in blood. So instead of travelling freely, cholesterol hitches a ride on lipoproteins — particles made of fat and protein that ferry it around your bloodstream. These are:

• LDL (low-density lipoprotein) — carries cholesterol from the liver to your cells

• HDL (high-density lipoprotein) — carries cholesterol back to the liver so it can be removed from the body

• VLDL (very-low-density lipoprotein) — the initial form the liver produces; it also carries triglycerides

LDL earned its "bad" reputation because higher levels are linked to a greater risk of cardiovascular disease. HDL is called "good" because it helps clear cholesterol from the system.

Over time, cholesterol — along with fat and calcium — can build up as plaque on artery walls, narrowing blood vessels and raising the risk of complications like stroke and heart attack. That's exactly why cholesterol shows up on a standard blood lipid test as part of assessing your cardiovascular risk.

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What about treatment?

In the UK, statins are among the most commonly prescribed medicines for managing cardiovascular disease risk — either as primary prevention (before any disease develops) or secondary prevention (for people who already have CVD).

Statins work by blocking an enzyme called HMG-CoA reductase, which reduces how much cholesterol your body produces in the first place.

One of the more talked-about side effects is myopathy — statin-related muscle aches — and, rarely, a more serious condition called rhabdomyolysis, where muscle tissue breaks down. One possible explanation is that statins also reduce coenzyme Q10, a substance made via the same pathway as cholesterol that's essential for cellular energy.

Extra caution is generally advised for people taking statins who also have type 1 diabetes, vitamin D deficiency, or undiagnosed hypothyroidism.

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It's never just about the number

Cholesterol doesn't exist in a vacuum. Levels are shaped by a mix of genetics, diet, lifestyle, underlying health conditions, and sometimes nutritional deficiencies. For instance, thyroid dysfunction can shift cholesterol levels — particularly in women and in men over 50 — and vitamin B12 deficiency has been linked to changes in how the body handles lipids.

That's why it's often more useful to zoom out rather than fixate on a single figure. Age, sex, genetics, diet, physical activity, body composition, smoking, alcohol intake, and other health conditions all contribute to your overall cardiovascular risk profile.

The QRISK3-lifetime tool can be used to estimate the overall CVD risk profile. Please note, CVD risk tool is a guide and may not always accurately reflect CVD risk. If you're unsure, speak to your GP for further advice.

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Is the science actually settled?

Not entirely. Observational studies can be affected by age, pre-existing illness, medication use, diet, and stress — and association doesn't automatically mean LDL is causing cardiovascular disease.

Speaking of stress: it's one more reason to keep it in check. Acute psychological stress can meaningfully raise cholesterol levels and contribute to atherosclerosis, while stress hormones like cortisol can affect blood pressure, inflammation, and clotting through pathways unrelated to LDL.

Some studies have even found a U-shaped relationship between LDL and mortality, where both very high and very low levels are linked to increased risk. Research from Danish and Japanese populations has also produced findings that don't fit neatly into the conventional narrative. The takeaway: it pays to look beyond LDL alone and consider the bigger picture of overall health.

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So, what can you actually do?

Managing cholesterol usually comes down to a combination of lifestyle choices and, where appropriate, medication:

• Move regularly — aerobic exercise like walking, paired with muscle-strengthening activity, can improve cholesterol levels and overall heart health

• Rethink your fats — swap saturated fats for monounsaturated and polyunsaturated fats, including omega-3 and omega-6

  • Omega-3: oily fish like salmon, chia seeds, walnuts

  • Omega-6: soybean oil, sunflower oil, various nuts

• Look at the whole picture — maintaining a healthy weight, avoiding smoking and excess alcohol, prioritising sleep, and checking triglyceride and thyroid status, all matter when assessing your CVD risk.

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Busting a few popular myths

• "Eggs raise cholesterol." For most healthy people, the body adjusts to dietary cholesterol; eggs are generally fine.

• "All fat is bad fat." Not true — saturated and trans fats are the main culprits, not fat as a whole.

• "High cholesterol only happens to people who are overweight." Anyone can have high cholesterol. Genetics play a huge role — conditions like familial hypercholesterolemia can cause elevated LDL from childhood.

• "It's just an age thing." Levels do tend to rise with age, but the damage to blood vessels can build up silently over decades — which is exactly why it's worth paying attention early.

 

The bottom line: your cholesterol number is one piece of a much bigger puzzle. Understanding how it fits alongside your genetics, lifestyle, and overall health is far more useful than fixating on a single figure from a blood test. 

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References 

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Finnikin, Sam, et al. “Statins, Risk, and Personalised Care.” BMJ, vol. 384, no. 384, 18 Mar. 2024, p. e076774, https://www.bmj.com/content/384/bmj-2023-076774?ijkey=7c3bb75ef5342767c01f381b384da3823c011356&keytype2=tf_ipsecsha, 10.1136/bmj-2023-076774. Accessed 9 July 2026.

Helmer, Jodi. “Everything You Thought You Knew About Cholesterol Is Wrong.” AARP, 20 Feb. 2015, https://www.aarp.org/health/healthy-living/cholesterol-myths/?msockid=0e5669db350d62ad049c7964342a6368. Accessed 8 July 2026.

Newman, Tim. “9 Myths About Cholesterol.” Www.Medicalnewstoday.Com, 24 Sept. 2021, https://www.medicalnewstoday.com/articles/medical-myths-all-about-cholesterol. Accessed 8 July 2026.

Ravnskov, Uffe, et al. “LDL-C Does Not Cause Cardiovascular Disease: A Comprehensive Review of the Current Literature.” Expert Review of Clinical Pharmacology, vol. 11, no. 10, 3 Oct. 2018, pp. 959–970, https://www.tandfonline.com/doi/full/10.1080/17512433.2018.1519391, 10.1080/17512433.2018.1519391. Accessed 13 July 2026.

Scudeler, Thiago Luis, et al. “Association Between Low-Density Lipoprotein Cholesterol Levels and All-Cause Mortality in Patients with Coronary Artery Disease: A Real-World Analysis Using Data from an International Network.” Scientific Reports, vol. 14, no. 1, 25 Nov. 2024, https://www.nature.com/articles/s41598-024-80578-w#abs1, 10.1038/s41598-024-80578-w. Accessed 23 July 2026.

Yaghoubi, Dadmehr, and Tamer Sallam. “Pushing the Limits of LDL Cholesterol: Emerging Paradigms in Cardiovascular Risk Reduction.” Trends in Cardiovascular Medicine, 13 July 2025, https://www.sciencedirect.com/science/article/pii/S1050173825000945, 10.1016/j.tcm.2025.07.002. Accessed 8 July 2026.