Atherogenic index of plasma

Your triglycerides are the fat your liver sends round from the sugar, fat and alcohol you took in, and your HDL are the particles that bring cholesterol back out of the vessel wall. With belly fat and insulin resistance those two move against each other: the triglycerides rise and the HDL falls. The atherogenic index of plasma catches those two movements in one number, by dividing the triglycerides by the HDL and taking the logarithm of the result. That logarithm is the only difference from the ordinary triglyceride/HDL ratio, and it mainly changes how the result looks. A division above one becomes a positive number, a division below one becomes negative, and zero means your triglycerides and your HDL are exactly the same size. A negative result is therefore not a deficit but a property of the scale, and it is also the healthy side. Because the logarithm compresses large differences, a sizeable change in the division underneath looks modest on this scale. The index appears on no Dutch report; you calculate it with the calculator on this page, from triglycerides and HDL in mmol/L. The result has no unit and no agreed normal value: the paper that introduced the name in 2001 published no division, and whoever later devised categories for it chose them themselves. Below zero is the healthy side, and the lower, the better.

The index puts together the two fat values that respond most strongly to how you live. Triglycerides go down with less sugar, less alcohol, losing weight and exercise; HDL goes up with exercise, losing weight and stopping smoking. Anyone who changes their lifestyle therefore sees the index move on two sides at once, and that makes it a sensitive measure of the gain from that change. The second reason is that the combination says something the separate numbers say less sharply. High triglycerides with a low HDL is the fat pattern of belly fat and insulin resistance, the forerunner of type 2 diabetes, and it goes together with small, dense LDL particles that lodge more easily in the vessel wall. An index above zero is therefore an early signal that the sugar balance needs attention, often years before the fasting glucose moves. The honest limitation is that the index is mainly a research measure. In the Netherlands nobody prints it, the risk estimate works with LDL and non-HDL, and there is no agreed division: two studies from 2026 set their boundaries at 0.21 and 0.5, or derive their own boundary of 0.3661. So read the index as a summary of two numbers you already have, not as a result with a norm.

A low index is favourable, and below zero means only that your HDL is larger than your triglycerides. Being drawn fasting rather than non-fasting lowers the triglycerides and with them the index; anyone who drinks less sugar and alcohol, exercises and loses weight sees the numerator fall and the denominator rise; and a high HDL makes the denominator larger without anything changing about the triglycerides. With a low index always check whether LDL itself sits below the limit that fits your risk, because the index says nothing about that. A high index means your triglycerides sit above your HDL. The most common explanation first: having eaten or drunk recently, because triglycerides rise for hours after a meal while HDL stays still; belly fat and insulin resistance, the pattern in which the liver makes more triglycerides and HDL falls; type 2 diabetes, in which that same pattern is locked in; alcohol, which makes the liver produce extra triglycerides; and rarely oestrogen therapy, which lifts the triglycerides. Read the index beside the triglycerides and HDL themselves, because the same result belongs to several combinations, beside the triglyceride/HDL ratio, which is the same division without the logarithm, beside non-HDL and LDL, which the risk estimate works on, and beside fasting glucose and HbA1c, which show whether the sugar balance is already moving along.