LDL cholesterol too high as an athlete: what your value means

The test tells you how much cholesterol is travelling through your blood in LDL packages, in millimoles per litre (mmol/l). LDL stands for low-density lipoprotein, the name of that package. The higher the number, the more cholesterol is in circulation that can end up in the wall of your arteries.

In a routine blood test the lab does not measure your LDL directly. It works the value out from three values it does measure: your total cholesterol, your HDL and your triglycerides. The calculation, known as the Friedewald equation, takes the total, subtracts the HDL and then subtracts the triglycerides divided by 2.2. So an error in any of those three ends up in your LDL.

The equation goes wrong when triglycerides are high: above roughly 4.5 mmol/l it is invalid and most laboratories will no longer report a calculated LDL. With a low LDL combined with raised triglycerides it underestimates the true value. And a meal within a few hours of the draw pushes triglycerides up, which feeds straight into the final number.

That carries an immediately useful conclusion for a low-carbohydrate diet, which typically brings low triglycerides. The known weakness of the equation requires the opposite. So a high LDL alongside low triglycerides cannot be explained away as an arithmetic artefact: the number is most likely real.

More reliable routes exist. The Martin-Hopkins method replaces the fixed divisor with a person-specific factor, the Sampson-NIH equation holds to roughly 9 mmol/l of triglycerides, and a direct LDL assay measures the cholesterol in LDL particles itself. Direct assays are less well standardised between manufacturers, though, so two laboratories can report a different number for the same blood.

There is also a point of principle. LDL measures the cargo inside the particles and says nothing about how many there are. Atherosclerosis is driven by the number of particles entering the artery wall. You read that number better from non-HDL cholesterol, your total cholesterol minus your HDL, and from apolipoprotein B, the protein of which each of those particles carries exactly one. Neither needs a division, so neither can go off the rails.

A raised LDL tells you that more cholesterol is travelling in your LDL particles than the target allows.

First the mechanism, because fitness does not change it. Every LDL particle carries one apolipoprotein B and can enter the artery wall. The more of those particles pass through over the years, the more plaque accumulates. A low resting heart rate, a high VO2max and a low body-fat percentage do not alter that biology. Training protects your heart in many ways, but it does not make a raised particle burden harmless.

Then the phenomenon itself. A strongly high-fat, low-carbohydrate way of eating raises LDL and apolipoprotein B in a substantial minority, and the rise is typically largest in lean, insulin-sensitive, well-trained people. A recognisable pattern has even been described: a markedly raised LDL, a high HDL and low triglycerides in someone with a low body-fat percentage. That is exactly the profile many performing athletes see on a ketogenic or carnivore diet. What it means is not settled. The imaging studies in this specific group are small and short. They do not prove the pattern is safe, and they do not prove it is as harmful as the same LDL from another cause. What is certain is that the number is real, and that you have the conversation about it with a doctor who knows your full risk profile.

Then the line on the paper. The 3.0 mmol/l on this page is the general target of the NVKC, the Dutch society of clinical chemists. It is not a personal goal. The Dutch GP guideline for cardiovascular risk only sets a personal target when there is a reason to treat: below 2.6 mmol/l at high risk, and below 1.8 mmol/l after established cardiovascular disease up to and including age seventy. At low to moderate risk the guideline names no target and lifestyle advice is enough. An LDL of 2.8 is therefore an ordinary value for a healthy thirty-year-old and at the same time clearly too high for anyone who has already had a heart attack. Above 5.0 mmol/l the same guideline advises considering an inherited lipid disorder, and that applies when you are fit as well. The laboratory prints its own range on the report, 0 to 4.5 mmol/l in our case, and that is a lab convention.

For non-HDL cholesterol, which is often more reliable than LDL itself, the goal in the same guideline sits 0.8 mmol/l higher: below 2.6 mmol/l at very high risk and below 3.4 mmol/l at high risk.

Finally, a cause that goes unmentioned far too often: anabolic androgenic steroids raise LDL and can sharply lower HDL, most clearly with oral forms. Anyone using them, or who has used them, should say so when a lipid panel is assessed, because otherwise the diet gets the blame while the explanation lies elsewhere.

Draw in an ordinary week rather than an exceptional one. Right after an exhausting endurance session or a race your triglycerides and your HDL shift temporarily, and because your LDL is calculated from those values, your LDL shifts with them. A panel taken the morning after a marathon mostly measures your marathon. Schedule the draw in a regular training week instead, and keep the timing consistent on a repeat so you are comparing like with like.

On fasting: total cholesterol, HDL, non-HDL and apolipoprotein B do not require it. Your triglycerides are meal-sensitive, and so, by extension, is the calculated LDL. If you want to follow your LDL over time, draw fasted and stick to it.

If you have changed your diet substantially, for example to a low-carbohydrate or ketogenic pattern, give your body at least six to twelve weeks before drawing conclusions from a new result. Test straight after the switch and you measure the transition rather than your new baseline.

There are also moments to wait. After surgery, an injury with prolonged inactivity or a significant infection, LDL falls for weeks, so a panel gives you a rosier picture than is warranted. Wait a few weeks after recovery.

If your LDL is unexpectedly high, have an underlying cause ruled out before you start rebuilding your diet. An underactive thyroid is the classic, easily missed explanation and is excluded with a TSH test. Poorly controlled diabetes, kidney disease, cholestasis and various medicines can raise the value too.