Atherogenic Index of Plasma (AIP)
The atherogenic index of plasma is the logarithm of the triglyceride-to-HDL-cholesterol ratio, a single number that reflects how atherogenic the blood lipid pattern is; it rises with obesity and insulin resistance.
Plain English
Patient-Friendly Explanation
The atherogenic index of plasma is worked out from two results on an ordinary cholesterol blood test. The triglyceride level is divided by the HDL cholesterol level, and the logarithm of that figure is then taken, which simply squeezes a wide range of numbers onto a smaller, easier scale. Triglycerides are the fat particles that rise when there is too much fat around the internal organs or too much refined carbohydrate in the diet, and HDL cholesterol is the protective fraction that helps clear cholesterol from the artery walls. Putting the two together gives one number that describes how unfavourable the balance is. Because the index also tracks the size of LDL particles, and small dense LDL particles are the ones that lodge in artery walls, it is a reasonable summary of heart and metabolic risk. In a study of more than six thousand Chinese adults, people in the top quarter of the index were several times more likely to be obese than those in the bottom quarter, and the index predicted obesity more accurately than triglycerides or HDL cholesterol on their own. In people with type 2 diabetes it identified metabolic syndrome accurately, and a large review of reviews found higher values in people with metabolic syndrome, type 2 diabetes and obstructive sleep apnoea. It needs no extra test and no extra cost, because a lipid panel is already part of the assessment. It is not a diagnosis and it does not measure body fat directly, and cholesterol-lowering medicines change it independently of weight, so it is read alongside the waist measurement and the other blood results.
Medical
Clinical Definition
The atherogenic index of plasma (AIP) is defined as the logarithm of the molar ratio of triglycerides to HDL cholesterol (AIP = log10 TG/HDL-C) and was introduced by Dobiásová and Frohlich as a practical surrogate for the atherogenic lipoprotein phenotype. Their work showed that AIP correlates closely with LDL particle size (r approximately 0.8) and with the rate of cholesterol esterification in apolipoprotein B-depleted plasma (r approximately 0.9), both established measures of atherogenic risk. Conventional risk bands are below 0.11 (low), 0.11 to 0.21 (intermediate) and above 0.21 (increased cardiovascular risk). In a population-based cross-sectional study of 6,465 Chinese adults aged over 30 years, the adjusted odds ratios for obesity across ascending AIP quartiles were 2.57, 3.77 and 6.21 (P for trend below 0.01), and substituting AIP for triglycerides and HDL cholesterol in the prediction model improved the area under the curve from 0.706 to 0.717. In a cross-sectional study of adults with type 2 diabetes, each one standard deviation increase in AIP carried a metabolic syndrome prevalence ratio of 1.31 (95% CI 1.15 to 1.47), the area under the curve for metabolic syndrome was 0.840, and the optimal cut-off was about 0.161. An umbrella review of meta-analyses reported higher AIP in metabolic syndrome (standardised mean difference 0.78), type 2 diabetes (1.78) and obstructive sleep apnoea (0.71), but not in steatotic liver disease. Cut-offs are not standardised across populations, and the index is altered by lipid-lowering therapy, alcohol, acute illness and thyroid disease, so it is interpreted with waist circumference, HbA1c, blood pressure and liver assessment rather than on its own.
Key Insight
Why It Matters
The index is useful in a weight clinic because it turns two values from a routine lipid panel into a single tracking number that moves with visceral fat and insulin sensitivity. It helps when weight is falling slowly while the metabolic profile is improving, and it flags a visceral-fat pattern in people whose body mass index looks acceptable. It does not measure body fat itself, it is not a diagnosis, and it should not be used to judge progress in someone taking a lipid-lowering medicine, because treatment shifts the ratio independently of body weight.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
