How to Prepare for an HDL and LDL Cholesterol Test
A cholesterol test is one of the most common blood tests in the UK, whether as part of an NHS Health Check, a sports medical or monitoring of a medicine. HDL and LDL results can influence decisions about statins and lifestyle advice for years, so it is worth making sure they reflect your usual state. Here is how to prepare, according to current UK and European practice.
What the test measures
A standard lipid profile, sometimes called a lipid panel, usually reports total cholesterol, HDL cholesterol, non-HDL cholesterol and triglycerides. LDL cholesterol is often calculated rather than measured directly, using equations such as the Friedewald formula or newer methods like the Martin–Hopkins approach.
HDL (high-density lipoprotein) carries cholesterol away from the tissues back to the liver, and higher levels have traditionally been seen as protective. LDL (low-density lipoprotein) delivers cholesterol to tissues and is the main driver of atherosclerosis when present in excess.
In the UK, results are reported in millimoles per litre (mmol/L). Non-HDL cholesterol — total cholesterol minus HDL — has become a key measure in NICE guidance because it captures all the atherogenic particles, not just LDL, and does not require fasting.
Some clinics also measure apolipoprotein B or lipoprotein(a), which give extra information in people with a family history of early heart disease. These tests need no special preparation beyond what is described below.
Do you need to fast?
For many years patients were told to fast for 12 hours before a cholesterol test. A joint consensus statement from the European Atherosclerosis Society and the European Federation of Clinical Chemistry, published in 2016, concluded that fasting is not routinely required.
After a normal meal, total cholesterol, HDL and non-HDL change very little. Triglycerides rise modestly, which can slightly lower calculated LDL. For most people these differences do not change clinical decisions.
NICE guidance in England likewise accepts non-fasting samples for cardiovascular risk assessment. Fasting may still be requested if triglycerides were previously very high, if a precise LDL value is needed or if the same sample will be used to measure fasting glucose.
Always follow the instructions on your blood test form or from your surgery. If you are asked to fast, this usually means no food for 10–12 hours beforehand; water is allowed and you should take regular medicines unless told otherwise.
Practical preparation checklist
A few simple steps help make sure your result reflects your usual lipid levels rather than a short-term fluctuation.
- Keep to your normal diet in the days before the test; avoid crash dieting or unusual feasts.
- Avoid alcohol for at least 24 hours, and ideally 48 hours, as it can raise triglycerides.
- Postpone the test if you have an acute illness, infection or recent surgery — these can lower cholesterol temporarily for several weeks.
- Avoid very strenuous or unusually long exercise the day before, especially if your sample will also be used for liver or muscle enzymes.
- Drink water normally to avoid dehydration, which can concentrate the blood.
- Bring a list of all medicines and supplements, including hormones, to the appointment.
If a result is unexpected, many clinicians repeat the test after a few weeks rather than acting on a single value, because day-to-day biological variation in lipids can be considerable.
Factors that change HDL and LDL
Several medicines and substances can shift lipid results. It is essential to mention them, because they change how the numbers should be interpreted.
| Factor | Typical effect |
|---|---|
| Regular aerobic exercise | Modest rise in HDL over months |
| Anabolic–androgenic steroids | Marked fall in HDL; LDL often rises |
| Isotretinoin and some antiretrovirals | Raised triglycerides and cholesterol |
| Hypothyroidism | Raised LDL |
| Pregnancy | Physiological rise in cholesterol and triglycerides |
| Statins, ezetimibe | Lower LDL and non-HDL |
A meta-analysis by Kodama and colleagues found that aerobic training raises HDL by a small but meaningful amount, with greater effects from longer weekly exercise time. These are gradual changes, not something achieved by a single session before a test.
Anabolic steroids, particularly oral compounds, can dramatically lower HDL. Hartgens and colleagues documented unfavourable changes in apolipoproteins in strength athletes using these drugs. Anyone using hormones without a prescription should tell the clinician honestly; the result cannot be interpreted correctly otherwise.
Understanding your results
NHS sources commonly use the following as healthy reference points for adults: total cholesterol of 5 mmol/L or below, non-HDL cholesterol of 4 mmol/L or below, LDL of 3 mmol/L or below and HDL above 1.0 mmol/L in men and above 1.2 mmol/L in women. Fasting triglycerides are ideally below 1.7 mmol/L.
These numbers are not treatment thresholds on their own. In the UK, decisions about statins are based on your overall cardiovascular risk, usually calculated with the QRISK3 tool, which takes into account age, sex, ethnicity, blood pressure, smoking, diabetes and family history as well as cholesterol.
Very high results — for example total cholesterol above 7.5 mmol/L, particularly with a family history of early heart disease — may suggest familial hypercholesterolaemia, an inherited condition that needs specialist assessment and family testing.
A very high HDL is not always protective, and a low HDL in a fit athlete may have different implications from the same value in a sedentary smoker. Discuss the whole picture with your GP rather than focusing on one figure.
Editorial conclusions
For most people in the UK, fasting is no longer needed before a cholesterol test; follow the instructions on your form if fasting is requested.
Avoid alcohol, unusual diets and very heavy exercise just before the test, and postpone it during acute illness. Be open about medicines, supplements and hormone use.
Interpret HDL, LDL and non-HDL values within your overall cardiovascular risk, and repeat unexpected results rather than reacting to a single sample.
Related topics you may find useful: blood tests while taking atorvastatin, how anabolic steroids affect lipids and how to prepare for a free T4 thyroid test.
References
- Nordestgaard BG, Langsted A, Mora S, et al. Fasting is not routinely required for determination of a lipid profile: clinical and laboratory implications including flagging at desirable concentration cut-points — a joint consensus statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine. Eur Heart J. 2016;37(25):1944–1958.
- National Institute for Health and Care Excellence. Cardiovascular disease: risk assessment and reduction, including lipid modification. NICE guideline NG238. London: NICE; 2023.
- Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;18(6):499–502.
- Martin SS, Blaha MJ, Elshazly MB, et al. Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile. JAMA. 2013;310(19):2061–2068.
- Kodama S, Tanaka S, Saito K, et al. Effect of aerobic exercise training on serum levels of high-density lipoprotein cholesterol: a meta-analysis. Arch Intern Med. 2007;167(10):999–1008.
- Hartgens F, Rietjens G, Keizer HA, Kuipers H, Wolffenbuttel BHR. Effects of androgenic-anabolic steroids on apolipoproteins and lipoprotein (a). Br J Sports Med. 2004;38(3):253–259.
- Mach F, Baigent C, Catapano AL, et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. Eur Heart J. 2020;41(1):111–188.
