The suprailiac region sits just above the iliac crest, the curved upper rim of your hip bone that you can feel by pressing your fingers into your side at waist level. In everyday terms, it is the soft tissue zone on your flank, roughly where a belt or waistband rests. The word itself breaks down simply: “supra” (above) and “iliac” (relating to the ilium, the large wing-shaped bone of the pelvis). Most people encounter this term in the context of body-fat testing, where a fold of skin and fat is pinched at this spot with calipers, but the suprailiac area is also relevant to pain syndromes, surgical procedures, and metabolic health risk assessment.
Where Exactly Is the Suprailiac Site
The iliac crest is the bony ridge you can trace from the front of your hip around toward your lower back. The suprailiac zone is the soft tissue sitting directly above this crest, predominantly on the side of the trunk. When fitness professionals or clinicians refer to a “suprailiac skinfold,” they typically mean a diagonal fold of skin grabbed just above the iliac crest along the midaxillary line, which is an imaginary vertical line running down from the center of your armpit. Some measurement protocols position the fold slightly more toward the front of the body, which is why you will sometimes see a distinction between “suprailiac” and “supraspinal” sites in standardized anthropometric systems.
This distinction matters more than it might seem. The International Society for the Advancement of Kinanthropometry (ISAK) protocol, widely used in sports science, measures both the suprailiac and supraspinal sites as part of an eight-skinfold profile that also includes biceps, triceps, subscapular, abdominal, front thigh, and medial calf.1PubMed Central. ISAK-Based Anthropometric Standards for Elite Male and Female Soccer Players When someone hands you a body-fat result based on skinfold calipers, the accuracy depends partly on whether the tester pinched the right spot and followed a consistent protocol. Grabbing the fold even a centimeter off can shift the reading, especially if you carry more tissue in that area.
Why the Suprailiac Fold Shows Up in Body-Fat Equations
Several of the most widely used body-composition prediction equations include the suprailiac skinfold as one of their measurement sites. The Jackson and Pollock equations, developed in the late 1970s and still among the most commonly applied formulas in gyms and university labs, use the suprailiac (listed as “suprailium”) as one of three sites for estimating body density in women, alongside triceps and thigh.2PubMed Central. Can we use the Jackson and Pollock equations to predict body density/fat of obese individuals in the 21st century? For men, the standard Jackson-Pollock three-site formula uses chest, abdomen, and thigh instead, though the suprailiac appears in the seven-site version used for both sexes.
The reason the suprailiac site was included in these equations is practical: it tends to reflect trunk fat accumulation with relatively manageable measurement error. Research on Japanese adults found that measurement errors in skinfold thickness grew with increasing obesity, but the suprailiac and abdominal sites showed smaller error increases compared to other locations, making them more reliable predictors of body density across a wider range of body sizes.3The Tohoku Journal of Experimental Medicine. Suprailiac or Abdominal Skinfold Thickness Measured with a Skinfold Caliper as a Predictor of Body Density in Japanese Adults In other words, the suprailiac fold stays relatively “well-behaved” as a measurement even when someone carries a lot of body fat, which is not true of every skinfold site.
How Accurate Are Skinfold Methods Compared to Lab Scans
Skinfold calipers, including measurements at the suprailiac site, are portable and cheap, but they consistently underestimate body fat compared to dual-energy X-ray absorptiometry (DXA), the lab method generally considered the reference standard. One study of active adults found that DXA measured average body fat at about 18.5% for males and 28.4% for females, while skinfold-based estimates came in at roughly 12.4% and 20.8% respectively.4European Journal of Sport Science. Evaluation of body composition using three different methods compared to dual‐energy X‐ray absorptiometry That is a meaningful gap, particularly for women. However, the correlation between skinfold measurements and DXA was still strong, with multiple correlations above 0.90 for both sexes when three sites were used together, meaning skinfolds track changes in body fat well even if they undercount the absolute amount.
A separate study in an Anglo-Celtic Australian population found good agreement between DXA and skinfold methods, though the agreement declined as overall body fat increased.5International Journal of Obesity. Agreement of skinfold measurement and bioelectrical impedance analysis (BIA) methods with dual energy X-ray absorptiometry (DEXA) in estimating total body fat in Anglo-Celtic Australians The pattern is consistent across research: skinfolds work best for lean to moderately fat individuals and become less precise at higher fat levels. If you are getting calipers pinched at the suprailiac site in a gym, the number you receive is a useful tracking tool over time but probably underestimates your true body fat by several percentage points.
Which prediction equation the tester uses also matters. A study comparing several body-density equations in African American and Caucasian American women found that different formulas produced different levels of overestimation or underestimation when checked against DXA. The Durnin and Womersley equation, which uses four skinfold sites including the suprailiac, showed relatively small overestimation in both groups.6PubMed. Body fat percentage assessment using skinfold thickness agrees with measures obtained by DXA scan in African American and Caucasian American women The takeaway for anyone getting tested: ask which equation is being used, and understand that all skinfold-based results are estimates with a margin of error of a few percentage points.
The Suprailiac Skinfold as a Metabolic Health Marker
Beyond estimating total body fat, the suprailiac skinfold has emerged as a useful indicator of metabolic risk on its own. A study evaluating skinfold thickness and cardiometabolic risk factors in both sedentary and physically active adults found that the suprailiac and subscapular skinfolds were the strongest individual predictors of higher metabolic risk, outperforming other sites.7PubMed Central. Skinfold Thickness as a Cardiometabolic Risk Predictor in Sedentary and Active Adult Populations The sum of four skinfolds (biceps, triceps, subscapular, and suprailiac) was significantly associated with cardiovascular risk linked to abdominal obesity, insulin resistance risk, elevated blood sugar, and high triglycerides. The fact that the suprailiac fold ranked among the top individual predictors makes sense anatomically: it captures fat stored on the trunk, which is the type of subcutaneous fat most closely linked to the visceral fat deposits that drive metabolic disease.
What is striking is that these associations held even in the physically active group. Being fit does not erase the metabolic signal carried by trunk-site skinfolds. The researchers suggested that suprailiac and subscapular skinfold measurements could be used as an early screening tool for cardiometabolic risk in the general adult population, including people who exercise regularly.8PubMed Central. Skinfold Thickness as a Cardiometabolic Risk Predictor in Sedentary and Active Adult Populations If your trainer measures your suprailiac fold and finds it thick relative to your limb-site folds, that is worth paying attention to regardless of your fitness level.
How Sex, Ethnicity, and Hormones Shape Suprailiac Fat
Fat distribution is not uniform across people, and the suprailiac region is one of the places where differences show up most clearly. Sex hormones are major drivers. Research on transsexual individuals receiving cross-sex hormone therapy provides some of the clearest evidence: estrogen treatment in male-to-female transsexuals caused a significant increase in subcutaneous fat at all measured sites, while testosterone treatment in female-to-male transsexuals reduced subcutaneous fat at all sites.9PubMed. Effects of sex steroid hormones on regional fat depots as assessed by magnetic resonance imaging in transsexuals These findings confirm that sex steroids are important determinants of where fat accumulates, including the trunk and flank regions captured by the suprailiac measurement. A study on surgically postmenopausal monkeys further showed that the combination of estrogen and progestin increased fat deposition, particularly in subcutaneous depots.10International Journal of Obesity. Effects of hormone replacement therapy and social stress on body fat distribution in surgically postmenopausal monkeys
Ethnic variation in fat patterning also affects how suprailiac measurements should be interpreted. A study comparing fat distribution in Black and White Americans found lower suprailiac-to-subscapular skinfold ratios in both Black men and Black women, meaning that for a given amount of subscapular fat, Black individuals tended to carry relatively less fat at the suprailiac site.11The American Journal of Clinical Nutrition. Anthropometry in blacks: applicability of generalized skinfold equations and differences in fat patterning between blacks and whites This is one of the reasons why body-fat prediction equations developed on predominantly White populations can produce biased estimates when applied to other groups. The absolute number at the suprailiac site means something different depending on the overall pattern of fat distribution, which varies by ancestry.
Age adds another layer of complexity. Skinfold compressibility changes as people get older due to shifts in skin elasticity and the ratio of water to fat in subcutaneous tissue. Pediatric reference data developed from Turkish schoolchildren ages 6 to 18 showed that suprailiac skinfold thickness varies substantially by age and sex during growth, with different percentile curves for boys and girls.12PubMed Central. Four-site skinfolds thickness percentiles of schoolchildren and adolescents in Turkey In adults, the shift from subcutaneous to visceral fat storage that occurs with aging means that a relatively thin suprailiac fold in an older person does not necessarily mean low total body fat; the fat may simply have migrated deeper.
Nerve Entrapment and Pain Near the Iliac Crest
The suprailiac region is not just about fat measurement. It is also a clinically significant area for pain. The superior cluneal nerve, which provides sensation to the upper buttock, originates from the T12 through L3 spinal nerve branches and crosses over the iliac crest through a tunnel formed by the thoracolumbar fascia and the bone itself. That tunnel can pinch the nerve, a condition called superior cluneal nerve entrapment.13International Journal of Pain. Superior Cluneal Nerve Entrapment as Uncommon Cause of Buttock Pain Symptoms typically include low back pain, upper buttock pain, numbness, and an abnormal burning or tingling sensation. The medial branch of the nerve is the one most often affected.
Anatomical studies put the frequency of this tunnel arrangement at a little over half of specimens examined: on 56% of 109 sides dissected, at least one branch of the superior cluneal nerve passed through the osteofibrous tunnel. Entrapment was detected in roughly 2% to 13% of cadaveric samples, though the actual rate of clinically significant entrapment requiring surgery is lower.14Neurospine. Superior and Middle Cluneal Nerve Entrapment as a Cause of Low Back Pain The condition is considered underdiagnosed because its symptoms overlap with more common causes of low back pain, and many clinicians do not specifically test for it.
A related but distinct condition is iliac crest pain syndrome (ICPS), characterized by localized tenderness directly over the iliac crest. In one study, ICPS was present in a considerable fraction of low back pain patients and could be distinguished from other forms of low back pain by specific clinical features: localized pain was present in 73% of ICPS cases, pain reproduced by lumbar spine movements in 64%, and pain with hip movements in 53%.15PubMed. Iliac crest pain syndrome in low back pain: frequency and features By contrast, patients with low back pain from other causes showed these features in only 2% to 12% of cases per sign. If you have persistent pain right at the top of your hip bone, particularly pain that worsens with twisting or bending, ICPS or nerve entrapment is worth discussing with your doctor.
Surgical Procedures Involving the Suprailiac Area
The iliac crest is one of the most common sites for harvesting bone graft material, used in orthopedic and spinal surgery to promote bone healing. Because the suprailiac soft tissues sit right on top of this harvest site, they are directly affected by the procedure. One recognized complication is abdominal hernia, which can develop when the suprailiac repair breaks down or the abdominal wall is not adequately reattached to the bony crest after graft harvesting.16JBJS Case Connector. A Complication of Iliac Crest Bone Grafting: Abdominal Hernia Treated With Robotic Herniography These hernias occur through the Petit triangle, a natural weak point in the lateral abdominal wall just above the iliac crest. Even with this known risk, the overall incidence of herniation after iliac crest bone grafting remains fairly low, reported at roughly 5% to 7%.17Cirugía y Cirujanos. Bone mesh fixation for the treatment of suprailiac hernia. Report of two cases
The suprailiac area also serves as an access point for minimally invasive spinal surgery. In an early report on endoscopic retroperitoneal lumbar spine fusion, surgeons accessed the retroperitoneal space through a suprailiac incision, then used a balloon to enlarge the working area for anterior fusion of fractures from the T12 to L5 vertebral levels.18PubMed. First clinical experience with an endoscopic retroperitoneal approach for anterior fusion of lumbar spine fractures from levels T12 to L5 The location is advantageous because it allows the surgeon to reach the front of the spine without cutting through abdominal muscles or entering the abdominal cavity. For patients, a suprailiac approach generally means less postoperative pain and faster recovery compared to larger open incisions, though the technique requires specialized training and equipment.
Soft Tissue Properties and Pressure Tolerance
Anyone who wears a belt, a holster, or an insulin pump on their hip interacts with the mechanical properties of suprailiac soft tissue daily. Research measuring the continuous mechanical responses of abdominal soft tissue under compression found that stiffness varied significantly between states of muscle activation and relaxation, though the differences between anterior and lateral measurement regions were generally not significant.19PubMed Central. Soft tissue material properties based on human abdominal in vivo macro-indenter measurements This has practical implications for product design: a waistband pressing into the suprailiac area meets tissue that behaves differently depending on whether you are standing, sitting, or bracing your core. The compressibility and stiffness data from studies like this feed into ergonomic models used to design everything from body armor to medical device mounts that sit against the flank.
For people who use continuous glucose monitors or insulin pumps, the suprailiac area is sometimes used as an alternative insertion site. The relatively consistent subcutaneous depth and moderate fat pad thickness at this location make it viable, though comfort and adhesion can vary with body composition and activity level. If you find that sensors placed on your abdomen or arm get knocked off during exercise, the upper hip area is worth trying, though you should confirm with your device manufacturer that the site is approved for your specific model.