Inflammation Tests — CRP and hs-CRP
Inflammation is part of the body's natural defense system. When we are injured or develop an infection, the immune system responds by producing inflammation to help protect and repair tissues.
But inflammation can also persist at low levels for months or years, even when we feel perfectly well. This is called chronic low-grade inflammation, and it has been associated with cardiovascular disease, insulin resistance, type 2 diabetes, and other chronic conditions.
Two blood tests, CRP and hs-CRP, can help detect inflammation. Understanding what they measure—and what they cannot tell us—can make them useful tools for evaluating our health.
What Is C-Reactive Protein (CRP)?
C-reactive protein is produced primarily by the liver in response to inflammatory signals from the immune system.
When inflammation increases, CRP levels in the blood can rise substantially.
A conventional CRP test is often ordered when a doctor suspects significant inflammation caused by an infection, inflammatory disease, or tissue injury.
However, CRP does not reveal where inflammation is occurring or what is causing it.
What Is hs-CRP?
High-sensitivity C-reactive protein (hs-CRP) measures the same protein but can detect much smaller concentrations.
This makes it useful for identifying low-grade inflammation that may be associated with cardiovascular risk.
Unlike standard CRP testing, hs-CRP can distinguish between relatively low concentrations that might otherwise go undetected.
Both tests measure inflammation, but hs-CRP is generally more useful when assessing cardiovascular risk.
Understanding Your hs-CRP Results
The following categories have traditionally been used to interpret hs-CRP for cardiovascular risk:
Below 1.0 mg/L: Lower relative cardiovascular risk
1.0–3.0 mg/L: Average relative risk
Above 3.0 mg/L: Higher relative risk
These categories are not diagnoses. They describe statistical associations between inflammation and cardiovascular events.
Current cardiovascular prevention guidelines also recognize hs-CRP of 2.0 mg/L or higher as a risk-enhancing factor when evaluating certain patients.
If hs-CRP is above 10 mg/L, doctors often consider infection, injury, or another active inflammatory condition and may repeat the test after recovery.
A single elevated result should not be interpreted in isolation.
Why Does Inflammation Matter for Heart Disease?
For many years, cardiovascular risk assessment focused heavily on cholesterol levels.
Researchers now recognize that inflammation also plays an important role in the development and progression of atherosclerosis—the accumulation of plaque in artery walls.
Inflammation can contribute to plaque development and instability, potentially increasing the likelihood of a heart attack or stroke.
Studies have found that people with elevated hs-CRP sometimes have increased cardiovascular risk even when their LDL cholesterol is not particularly high.
Clinical trials of certain anti-inflammatory treatments have also demonstrated reductions in cardiovascular events, providing evidence that inflammation is more than simply a marker of risk.
However, lowering CRP itself is not necessarily the same as lowering cardiovascular risk.
What About Metabolic Health?
Chronic low-grade inflammation is often associated with:
Insulin resistance
Abdominal obesity
Type 2 diabetes
Metabolic dysfunction
Fatty liver disease
Excess visceral fat—the fat surrounding internal organs—can contribute to inflammatory signaling.
Improving metabolic health through exercise, dietary changes, weight management when appropriate, and better sleep may help reduce inflammation.
For people following a low-carbohydrate diet, improvements in insulin resistance and abdominal fat may be accompanied by reductions in hs-CRP. However, results vary, and not every low-carbohydrate diet produces the same effects.
Can hs-CRP Tell Us Whether We Are Healthy?
Not by itself.
A low hs-CRP level does not guarantee healthy arteries, and a higher result does not necessarily indicate cardiovascular disease.
CRP can rise because of infections, autoimmune diseases, injuries, and other inflammatory conditions.
It is also affected by smoking, obesity, certain medications, and other factors.
The most useful interpretation comes from considering hs-CRP alongside blood pressure, glucose, cholesterol, ApoB when appropriate, smoking history, and other cardiovascular risk factors.
Should Older Adults Have hs-CRP Testing?
For people in their 50s and 60s, hs-CRP may be particularly useful when cardiovascular risk is uncertain and the result could influence a treatment decision.
For adults in their 70s and 80s, interpretation becomes more individualized. Age, existing cardiovascular disease, medications, frailty, and other health conditions may be more important than a single inflammatory marker.
Routine hs-CRP screening is not recommended for everyone.
But when cardiovascular risk remains uncertain, it can sometimes provide another useful piece of information.
What Can We Do About Chronic Inflammation?
Several lifestyle approaches have evidence supporting their ability to reduce chronic inflammation or improve the conditions associated with it.
These include regular physical activity, resistance exercise, avoiding smoking, adequate sleep, improving metabolic health, and eating a nutritious diet that minimizes highly processed foods.
Treating underlying inflammatory diseases is also important.
There is no compelling evidence that everyone should take supplements or medications simply to lower a mildly elevated hs-CRP result.
The Bottom Line
CRP and hs-CRP are useful markers of inflammation, but they do not identify its cause.
hs-CRP is particularly interesting because it connects inflammation with cardiovascular and metabolic health.
It can add information to traditional cardiovascular risk assessment, especially when treatment decisions are uncertain.
But like most blood tests, it is most valuable when interpreted in the context of a person's overall health rather than as an isolated number.
Learn More
Ben Bikman explains how chronic inflammation can interfere with insulin signaling, contributing to insulin resistance and metabolic disease. He discusses how inflammatory processes, stress hormones, and elevated insulin interact, providing a useful connection between inflammation and metabolic health.
A clear explanation from the National Library of Medicine of what CRP measures, why doctors order the test, and how conventional CRP differs from hs-CRP.
The updated guidelines recognize persistently elevated hs-CRP (2 mg/L or higher) as a factor that can help refine cardiovascular risk assessment.
This landmark randomized trial involving more than 10,000 patients with previous heart attacks found that a targeted anti-inflammatory medication reduced recurrent cardiovascular events without lowering LDL cholesterol. However, it also increased the risk of serious infections.