hs-CRP

Cholesterol tells you how much flammable material is in the building. It says nothing about whether anything is actually on fire.

Plenty of people have a clean lipid panel and a smoldering problem anyway. Their blood vessels are inflamed, their plaque is the unstable kind, their tissues are aging faster than their numbers suggest, and none of it shows up on a standard panel. Inflammation is the process underneath an enormous share of chronic disease, from heart attacks to diabetes to dementia, and for most of a lifetime it makes no noise at all.

hs-CRP is the most accessible way to listen for it. The "high-sensitivity" part is the whole point: ordinary CRP testing is built to detect the roaring inflammation of an infection, while the high-sensitivity assay picks up the faint, persistent signal of the low-grade inflammation that drives long-term disease. A standard panel measures the fuel. This one checks for smoke ^[1].

C-reactive protein is made by the liver, and it is produced on demand in response to a signaling molecule called interleukin-6. When immune cells anywhere in the body encounter damage or infection, they release interleukin-6 into the blood, the liver receives that signal, and within hours it ramps up CRP production ^[2]. CRP then circulates and binds to the surfaces of dying cells and pathogens, flagging them for removal and activating the broader immune response.

This makes CRP a faithful summary of total inflammatory load. It does not measure any single source. It integrates all of them, which is exactly what makes it useful: a single number reflecting how much inflammatory signaling your body is doing right now.

The high-sensitivity assay matters because the levels that predict chronic disease are very low, often well under 1 mg/L, far below what older CRP tests could reliably read. At these concentrations, the number reflects the background hum of inflammation rather than any acute event. The usual sources of that hum are familiar: visceral fat, which behaves like an inflammatory organ and secretes interleukin-6 directly; insulin resistance; a diet high in refined carbohydrate; smoking; poor sleep; gum disease; and the slow, generalized rise in inflammatory tone that accompanies aging itself, sometimes called inflammaging ^[3].

Inflammation is also meant to switch off once its job is done, and that resolution is an active process, not just the absence of a signal. The omega-3 fatty acids EPA and DHA supply the raw material for the specialized molecules that carry it out, which is part of why a higher omega-3 status tends to track with a lower CRP ^[4].

The link between low-grade inflammation and cardiovascular events is one of the most replicated findings in the field. In a meta-analysis pooling more than 160,000 people without a history of vascular disease, each increment of hs-CRP tracked with a higher risk of coronary heart disease, ischemic stroke, and vascular death ^[1]. The association persisted across populations and held even among people whose cholesterol was unremarkable.

That last point reframed how risk is understood. Lowering atherogenic particles is essential, but a meaningful share of cardiovascular events still occurs in people whose lipids are well managed, and elevated inflammation identifies much of that remaining risk. This is the concept of residual inflammatory risk: two people with identical cholesterol can carry very different danger, and inflammation is part of what separates them ^[3].

CRP's strength and its weakness are the same trait. Because it integrates inflammation from every source, it is sensitive but not specific. A value above roughly 10 mg/L usually signals an acute event, a cold, an injury, a flare of something, rather than chronic cardiovascular risk, and the test should simply be repeated once recovered. The meaningful screening range sits below that, where a persistently elevated reading points to a chronic, modifiable process. Whether CRP itself drives damage or mainly marks the interleukin-6 pathway that does is still debated, but for practical purposes it does the job that matters: it tells you the fire is lit, early enough to do something about it.