How to prepare for the 'HDL and LDL' test: rules for taking it

High-density (HDL) and low-density (LDL) lipoproteins are the basis of the lipid profile used to assess cardiovascular risk. For an athlete who uses hormonal drugs or simply monitors their health, this is one of the most important indicators. But the result is easily distorted by improper preparation. The editorial team explains what really affects the numbers and how to take the test so that it can be compared over time.

What exactly the test measures

Cholesterol does not dissolve in water, so in the blood it is carried within lipoproteins — particles with a protein shell and a fatty core. LDL delivers cholesterol to tissues and is considered the main atherogenic class: it is precisely these that penetrate the artery wall and form plaque. HDL, on the contrary, participates in the reverse transport of cholesterol to the liver.

The laboratory report usually shows not the number of particles but the cholesterol content within them: LDL-C and HDL-C. HDL cholesterol is measured by a direct method. LDL cholesterol is still calculated by many laboratories using the Friedewald formula from total cholesterol, HDL and triglycerides, while others use a direct homogeneous method or the newer Martin–Hopkins or Sampson formulas.

This nuance is important for preparation. Calculated LDL depends on the triglyceride level, and triglycerides react most strongly to food, alcohol and recent exertion. That is why an error in preparation often hits LDL specifically, even though a person thinks that «cholesterol does not change from breakfast».

It is also worth remembering variability: even with ideal preparation, one person's lipid values fluctuate by a few percent from week to week. Therefore a single result that deviates slightly from the norm is no cause for panic, and it is better to compare trends within the same laboratory using the same method.

Fasting or not: what current guidelines say

The classic rule is to take a lipid profile after 12 hours of fasting. However, in 2016 the European Atherosclerosis Society and the European Federation of Clinical Chemistry published a joint consensus stating that for routine risk assessment the test can also be taken without fasting. The authors relied on data from large population studies with hundreds of thousands of participants.

After an ordinary meal the values change insignificantly: the average triglyceride level rises by about 0.3 mmol/L, total cholesterol and LDL-C decrease by about 0.2 mmol/L, while HDL-C practically does not change. For assessing risk in a population, such shifts are not decisive.

At the same time, the consensus does not abolish fasting tests entirely. Fasting is recommended if triglycerides in a previous non-fasting test exceeded 5 mmol/L, in known hypertriglyceridemia, during the monitoring of a patient with pancreatitis, and also when a precise comparison with previous results obtained while fasting is needed.

The editorial position is practical: if you are tracking trends — for example, before and after a change in diet or a course of drugs — take the test each time under identical conditions. The simplest standard is in the morning, after 10–12 hours without food, with plain water permitted. This way the results will be comparable with one another.

Factors that distort the result

The most powerful «external» factor is alcohol. Even a moderate amount the night before can raise triglycerides and, through them, shift calculated LDL. That is why alcohol should be avoided for at least 24–48 hours before the test, and after a feast with a large amount of fatty food it is better to postpone the test for a few days.

The second group is acute conditions. After an infection with fever, an injury, surgery or an acute cardiovascular event, cholesterol levels temporarily decrease, and HDL can drop substantially. A result obtained during illness does not reflect the usual lipid profile, so a routine lipid profile is usually postponed until full recovery, roughly for a few weeks.

The third group is medications and hormones. Statins, ezetimibe, fibrates and high-dose omega-3 deliberately alter lipids. Beta-blockers, thiazide diuretics, isotretinoin, corticosteroids and combined oral contraceptives can also affect the values. Drugs prescribed by a doctor must not be discontinued before the test — it is enough to note them on the referral.

Finally, technical details. Prolonged tourniquet application and changing body position from lying to upright can «concentrate» the blood by a few percent. Therefore, before the draw it is advisable to sit for 10–15 minutes, not smoke for at least an hour before the test, and not arrive at the laboratory after a run or after climbing the stairs quickly.

Considerations for athletes

Regular aerobic training in the long term raises HDL-C and lowers triglycerides — this is one of the proven effects of physical activity. But a single intense or very prolonged training session the day before produces short-term changes that do not reflect the baseline state. Therefore, for 24–48 hours before the test it is worth limiting yourself to light activity.

A special situation is the use of anabolic androgenic steroids. Reviews by the Endocrine Society describe a pronounced decrease in HDL-C and often an increase in LDL-C with supraphysiological doses, with oral 17-alpha-alkylated drugs affecting lipids especially strongly. Such a profile is associated with an increased risk of atherosclerosis.

For correct interpretation it is important for the doctor to know whether the test was taken during drug use, immediately after, or several months after completion. The lipid profile gradually recovers after discontinuation, so a result without the time context can be misleading. The editorial team advises honestly reporting all drugs and supplements to the doctor.

Regarding dietary supplements: plant sterols, soluble fiber and fish oil in dietary doses can moderately affect lipids. If you have started a new regimen, it is logical to take a follow-up test no earlier than 6–8 weeks later, when the effect stabilizes, and not to change other habits during this period.

Preparation checklist and interpretation

We have gathered the main rules into a short list that is convenient to save before a visit to the laboratory:

• 2–3 days before — your usual diet without «cleanses» and feasts;
• 24–48 hours before — no alcohol and no exhausting workouts;
• for tracking trends — 10–12 hours without food, water permitted;
• in the morning, before 10–11 o'clock, no smoking for at least an hour;
• before the draw — sit quietly for 10–15 minutes;
• note on the referral all medications, hormones and supplements.

Once you receive the result, look at target values, not only the laboratory's «reference range». European guidelines on dyslipidemia define the target LDL-C depending on overall cardiovascular risk: the higher the risk, the lower the target. For low risk the benchmark is a level below 3.0 mmol/L, for very high risk — significantly lower values.

For HDL-C, a level below 1.0 mmol/L in men and below 1.2 mmol/L in women is usually considered low. However, modern guidelines do not recommend artificially «raising» HDL as a treatment goal: the main modifiable risk factor remains LDL and other apoB-containing particles.

If triglycerides are high, calculated LDL becomes unreliable: the Friedewald formula is incorrect at triglycerides above 4.5 mmol/L. In such a situation it is useful to request direct LDL, calculation of non-HDL cholesterol, or an apolipoprotein B test.

Editorial conclusions

For a one-time risk assessment, a lipid profile can also be taken without fasting, but for tracking trends it is worth adhering to identical conditions: morning, 10–12 hours without food, no alcohol and no heavy workouts the day before.

Most often the result is distorted not by breakfast but by alcohol, acute illness, intense exertion and unaccounted-for use of medications or hormones.

For athletes who use hormonal drugs, a lipid profile is especially necessary: a drop in HDL and a rise in LDL is one of the most frequent and least noticeable side effects.

We also recommend reading our materials on preparing for the triglyceride test, on apolipoprotein B as a more precise marker of atherogenic particles, and on monitoring heart health during strength training.

References

1. 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.
2. 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.
3. 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.
4. 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.
5. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC guideline on the management of blood cholesterol. J Am Coll Cardiol. 2019;73(24):e285–e350.
6. Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.