High-sensitivity CRP (hs-CRP) is a blood test that measures very low levels of C-reactive protein, a substance your liver produces in response to inflammation. Unlike a standard CRP test, which detects the large spikes in inflammation caused by serious infections or injuries, the high-sensitivity version is designed to pick up the subtle, chronic inflammation linked to heart disease risk. The key difference is precision: a standard CRP test starts measuring at about 5 mg/L, while hs-CRP can detect levels below 1.0 mg/L.
How It Differs From a Standard CRP Test
CRP and hs-CRP measure the exact same protein. The “high sensitivity” label refers to the test’s ability to detect much smaller amounts of it. During a serious infection, CRP levels can surge to 500 mg/L, making it easy for a standard test to pick up. But the low-grade inflammation that slowly damages arteries produces CRP levels far below 10 mg/L, often in the 1 to 3 mg/L range. Standard tests simply aren’t sensitive enough to distinguish between those small differences. The hs-CRP test has a detection limit of about 0.15 mg/L, roughly half that of standard CRP, allowing it to sort people into meaningful risk categories.
If your doctor ordered an hs-CRP test specifically, they’re almost certainly interested in your cardiovascular risk rather than looking for an active infection or acute illness.
What Your Results Mean for Heart Disease Risk
The widely used risk categories for hs-CRP are straightforward:
- Below 1.0 mg/L: Lower relative risk of future heart disease
- 1.0 to 3.0 mg/L: Moderate risk
- Above 3.0 mg/L: Higher risk
These thresholds exist because chronic, low-level inflammation plays a central role in atherosclerosis, the buildup of plaque inside your arteries. Inflammation helps recruit immune cells to artery walls, contributes to plaque growth, and can eventually destabilize plaques enough that they rupture. When that happens, a blood clot forms, potentially causing a heart attack or stroke. An elevated hs-CRP level doesn’t mean you have plaque buildup right now. It signals that the kind of systemic inflammation associated with that process is present in your body.
Joint guidelines from the American Heart Association and CDC recommend hs-CRP testing primarily for people at intermediate cardiovascular risk, meaning a 10% to 20% estimated chance of heart disease over the next 10 years. For these patients, the result can help tip a borderline risk assessment in one direction and guide decisions about preventive treatment. It’s not recommended as a standalone screening tool for everyone, and it shouldn’t be used to guide treatment decisions during an acute cardiac event.
What Can Falsely Raise Your Results
Because CRP responds to any kind of inflammation, many things besides cardiovascular risk can push your hs-CRP above 3.0 mg/L. A recent cold, a dental infection, a pulled muscle, or even a bad night’s sleep can cause a temporary bump. Periodontal disease (chronic gum inflammation) is a common and often overlooked cause of mildly elevated results. Depression, pregnancy, obesity, diabetes, cigarette smoking, and exposure to air pollution all tend to raise baseline CRP levels as well.
This is why a single elevated reading shouldn’t be over-interpreted. Many doctors will repeat the test after a few weeks, ideally when you’re free of any obvious illness or injury, to get a more reliable picture. The test also comes with a practical preparation step: avoid intense exercise like heavy weight training or a long run beforehand, as these can cause a short-term spike in CRP. Fasting is generally not required.
Non-Cardiac Causes of Elevated hs-CRP
If your hs-CRP is persistently elevated and your cardiovascular risk profile doesn’t fully explain it, other chronic conditions could be driving the inflammation. Autoimmune diseases like rheumatoid arthritis, lupus, and vasculitis are common culprits. Inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis, frequently raise CRP. Lung conditions such as asthma can contribute too. Bacterial and viral infections cause the most dramatic CRP elevations, but even lingering low-grade infections can keep levels modestly high.
About 75% of obese individuals have hs-CRP levels at or above 1.0 mg/L, which places them in at least the moderate cardiovascular risk category by that measure alone. This reflects the fact that excess body fat, particularly visceral fat around the organs, is itself a source of chronic inflammation.
What Can Lower Elevated hs-CRP
Lifestyle changes are the first line of defense. Weight loss in people who are overweight tends to bring CRP down because it removes a major source of ongoing inflammation. Regular moderate exercise, quitting smoking, and managing conditions like diabetes and gum disease all reduce inflammatory burden over time.
Some specific interventions have been studied directly. In a clinical trial of moderately overweight nonsmokers with hs-CRP at or above 1.0 mg/L, taking 1,000 mg of vitamin C daily for two months reduced CRP by about 25% compared to a placebo. Cholesterol-lowering statin medications also lower CRP, though the effect is modest. Across several large trials, statins reduced CRP by roughly 14% to 17% over treatment periods ranging from one to five years. Vitamin E showed some reduction in trials but the effect wasn’t statistically significant.
It’s worth noting that the AHA guidelines explicitly advise against using serial hs-CRP measurements to monitor whether a treatment is working. The test fluctuates enough on its own that small changes between readings may not reflect real improvement. Instead, hs-CRP is best understood as one piece of a broader cardiovascular risk picture, useful for making initial decisions about prevention rather than tracking progress over time.