High cholesterol: the numbers that matter and what to do about your real risk

A high cholesterol result is worrying, but the number alone says little. What matters is which fraction is high, what your cardiovascular risk is, and what has been shown to work for someone like you. This guide sets it out using current European guidelines, with numbers in both mmol/L, as UK and Nordic GPs report them, and mg/dL, as most Spanish labs do.

Which cholesterol matters

Cholesterol travels in the blood inside particles called lipoproteins. The ones that weigh most on your risk are LDL particles: they deposit cholesterol in artery walls and cause atherosclerosis. That is why LDL cholesterol is the main treatment target ^[3].

A full lipid profile includes total cholesterol, LDL, HDL and triglycerides. Non-HDL cholesterol and apolipoprotein B are sometimes added; they sharpen the estimate in people with high triglycerides or diabetes.

The blood test: no fasting, and lipoprotein(a)

For years you were told to fast. Routinely, you no longer need to. A 2016 European consensus found that after a normal meal the changes are small and clinically irrelevant: triglycerides rise by about 0.3 mmol/L (26 mg/dL) and LDL falls by about 0.2 mmol/L (8 mg/dL), while HDL and lipoprotein(a) do not change ^[1]. Only if non-fasting triglycerides are above 5 mmol/L (440 mg/dL) is the test repeated fasting ^[1].

Lipoprotein(a), or Lp(a), is the forgotten marker. It is a particle similar to LDL whose level depends mainly on your genes and changes little with lifestyle. A high level raises the risk of heart attack and of aortic valve narrowing, even when LDL is low. That is why the European Atherosclerosis Society and the European guidelines recommend measuring it at least once in adult life ^{[2] [3]}. Labs flag an Lp(a) of 50 mg/dL or more as raised, and above 150 mg/dL the risk is very high ^[1]. The 2025 update of the European guidelines strengthens its role in risk assessment ^[4].

Your risk comes before your number

The same LDL does not mean the same thing at 35 with no other risk factors as at 60 with diabetes and a smoking habit. European prevention guidelines estimate ten-year risk with SCORE2, and SCORE2-OP from 70 ^[5]. In the UK your GP will usually have used QRISK, so the percentages may not match.

That risk sets your LDL target ^[3]:

• Very high risk: below 1.4 mmol/L (55 mg/dL) and at least a 50% reduction.
• High risk: below 1.8 mmol/L (70 mg/dL).
• Moderate risk: below 2.6 mmol/L (100 mg/dL).
• Low risk: below 3.0 mmol/L (116 mg/dL).

What if you are already below target? The idea that going lower "adds nothing" does not hold up. A meta-analysis of 26 trials and 170,000 people showed that every 1 mmol/L (39 mg/dL) reduction in LDL cuts major vascular events by about 22%, with no threshold below which the benefit disappears ^[6]. The real question is how much absolute benefit each person gains, given their risk.