LDL/HDL Ratio: Not the Same as Your Cholesterol Ratio

The LDL/HDL ratio is one piece of division, nothing more. On the top line sits your LDL cholesterol. On the bottom line sits your HDL cholesterol. No extra tube of blood goes in. The lab takes two values that were already on your report and divides one by the other. With an LDL of 2.8 and an HDL of 1.4, your ratio is 2.0.

Now the point where almost everyone gets stuck. Two ratios exist in the cholesterol world, and they resemble each other only in name. Search for cholesterol ratio LDL HDL and you will see both jumbled together. The difference sits on the top line.

The cholesterol/HDL ratio divides your total cholesterol by your HDL. That total holds everything: the LDL, the HDL itself and whatever else is circulating. So the answer comes out higher and the limit sits higher. This page is about the other number, with only the LDL on the top line and a limit around 3.

Work it through once, on one tube of blood. Total cholesterol 5.4. HDL 1.2. LDL 3.6. The cholesterol ratio is 5.4 divided by 1.2, which is 4.5. The LDL/HDL ratio is 3.6 divided by 1.2, which is 3.0. One draw, two answers a point and a half apart. So a 4 anywhere on your report is tidy on one scale and too high on the other. Always check first which ratio you are looking at, and which upper limit the lab printed next to it.

The honest answer to which of the two ratios you should follow is: neither. They are not targets. The European guideline and the Dutch CVRM standard put their goals on LDL itself, with non-HDL cholesterol and ApoB behind it. No guideline names a limit for the LDL/HDL ratio. Your doctor does not treat you on it, and you do not need to steer by it at home either.

Every fraction leaks: afterwards you can no longer see which two numbers went into it. That sounds abstract, so do the sums with me.

Anna has an LDL of 3.0 and an HDL of 1.0. Divide 3.0 by 1.0 and you land on 3.0.

Bram has an LDL of 4.5 and an HDL of 1.5. Divide 4.5 by 1.5 and you land on 3.0 as well.

On paper the two reports say exactly the same thing. Now put the LDL values side by side: 4.5 against 3.0. That is a gap of 1.5 mmol/l. Bram walks around with half again as much harmful cholesterol as Anna, while their ratio matches to the decimal. His higher HDL wiped that gap out inside the division. And what can pile up in your artery wall over the years is that absolute LDL value, not the proportion.

The cholesterol ratio pulls the same trick: there too the separate values vanish into one answer. The LDL/HDL ratio breaks on a second point as well. Particles that are neither LDL nor HDL count nowhere. Think of VLDL and the leftovers that remain once VLDL has released its fat. Those carry cholesterol into the artery wall too. With high triglycerides you have more of them, and that is exactly when this number shows you the least.

So what should you use? Look at your LDL in mmol/l. If non-HDL cholesterol is on your report, let it weigh more than any ratio. You work non-HDL out like this: total cholesterol minus HDL. Everything that can do damage sits in there, including the particles this ratio skips. And if ApoB is listed, that counts the number of harmful particles rather than their cargo.

There is also no limit that fits everyone at once. What counts as an acceptable LDL depends on your age, your blood pressure, smoking, diabetes and what runs in your family. The little line on your report comes from the population, not from your situation. So discuss it with a doctor.

You do not order this number on its own. It falls out of a cholesterol panel automatically, as soon as the LDL and the HDL are known. So the real question is when you have such a panel taken, and under what conditions.

Fasting counts for more here than you would think. For total cholesterol and HDL, eating barely matters. But in most labs your LDL is not measured, it is estimated from your triglycerides. And triglycerides rise after a meal. The estimated LDL then comes out too low, which makes your ratio look prettier than it is. Above roughly 4.5 mmol/l of triglycerides that estimate stops working altogether. This is the cholesterol ratio's biggest advantage in one line: it uses two values the lab measures directly, so it does not have that problem.

Also wait a few weeks after surgery, a heavy infection or a heart attack. Your cholesterol dips temporarily in that period, and the result then paints a rosier picture than your usual situation.

Comparing two results? Allow for noise. Total cholesterol and LDL swing day to day by some five to ten percent, triglycerides by twenty to twenty-five percent. A small difference therefore usually means nothing.

Is your result new and abnormal? Then look for a cause before you blame your diet. An underactive thyroid raises LDL and is often overlooked, so have your TSH checked as well. Poorly controlled diabetes, kidney disease, liver disease, cholestasis, heavy drinking, pregnancy and a range of medicines (prednisone, oestrogen in tablet form, isotretinoin, diuretics, beta blockers, anabolic steroids) can equally explain the picture. Always take your result to a doctor, together with your individual values.