LDL / HDL Ratio

Cholesterol travels through your blood in particles, and those particles do two opposite things. LDL particles carry cholesterol to the tissues and lodge in the vessel wall on the way, where they form the plaques called atherosclerosis. HDL particles take cholesterol out of the vessel wall and bring it back to the liver. The LDL/HDL ratio divides one by the other, and the idea is that the balance between depositing and collecting says more than either alone: a high LDL is less bad with plenty of HDL alongside, and an average LDL weighs more heavily with little HDL. That idea holds up to a point, and that is where the limitation sits. A division turns two numbers into one number, and which two they were can no longer be read afterwards: a strongly lowered LDL with a low HDL gives the same ratio as an average LDL with a high HDL, and those are two different situations. Moreover LDL is the side you can steer with diet and medicines, and HDL much less; a high HDL also protects less than was long thought. That is why the Dutch risk estimate works not with this ratio but with LDL itself and with non-HDL, and treats on those numbers. Your report usually does not print the ratio; you calculate it with the calculator on this page. The result has no unit. The usual limits come from a review article: below 3.0 for a man and below 2.5 for a woman counts as the target, above 3.5 and 3.0 as increased risk. Anyone who eats well, exercises and does not smoke usually sits around 2 or lower.

The ratio is above all a way to read your lipid profile at a glance. Anyone with an LDL at the high end who wonders how bad that is sees from the ratio whether HDL sets something against it; anyone with a beautifully low LDL from a statin but a low HDL from belly fat and little exercise sees that the profile is not finished yet. And because the ratio moves on two sides at once, it often shows the gain of lifestyle earlier than LDL alone: losing weight and exercising lift HDL and lower LDL, and the ratio falls on both sides. The second reason is the conversation with the rest of your lipid profile. The same ratio can mean something quite different in two people, and the question is always which of the two numbers moved. A ratio that falls because HDL rose through more exercise is gain; a ratio that falls because LDL dropped through a statin while HDL stayed low is gain on one front. A ratio that rises because HDL fell through smoking or gaining weight is a different signal from a ratio that rises through more saturated fat. The honest limitation is that the ratio appears on no Dutch report and that the Dutch risk estimate does not work with it. The risk estimate works with LDL itself and with non-HDL, which counts all cholesterol in depositing particles together, and ApoB counts those particles directly. Anyone who wants to know their vascular risk reads those numbers; the ratio is the summary, not the verdict.

A low ratio is favourable, and the only question is how it got that low. Plant-based, fibre-rich eating, a healthy weight and plenty of exercise lower LDL and lift HDL, and that is the healthy route. Lipid-lowering medicines, a statin first of all, lower LDL specifically and bring the ratio down without HDL moving. A high HDL makes the denominator larger without anything changing about LDL, and then the same low ratio can hide an LDL that is too high in itself; so always check whether LDL itself sits below the limit that fits your risk. A high ratio means proportionally a lot of depositing and little collecting cholesterol is circulating. In order of how often it occurs: a lot of saturated fat in the diet, from fatty meat, full-fat dairy, butter, coconut fat and biscuits, which lifts LDL; excess weight and little exercise, which lower HDL and make the denominator smaller; an underactive thyroid, which slows the breakdown of LDL; and rarely familial hypercholesterolaemia, an inherited make-up in which LDL is high from childhood, recognisable by an LDL above 5 mmol/L and cardiovascular disease in the family at a young age. Smoking lowers HDL and so lifts the ratio. Always read the ratio beside LDL and HDL themselves, because the ratio does not say which of the two moved, beside non-HDL and ApoB, which count the depositing particles and which the risk estimate works on, and beside the triglycerides, because above 4.5 mmol/L the calculated LDL no longer holds.