CRP Test Explained: What C-Reactive Protein, hs-CRP and ESR Tell You About Inflammation

Quick answer: C-reactive protein (CRP) is made by the liver when there is inflammation or infection in the body. A standard CRP below about 5–10 mg/L (depending on the lab) is usually considered normal; mildly raised levels occur with minor infections or chronic inflammation, and very high levels (often above 100 mg/L) commonly indicate significant bacterial infection or severe inflammation. hs-CRP (high-sensitivity CRP) measures very low levels and is used to assess heart disease risk: below 1 mg/L low risk, 1–3 average, above 3 higher. ESR is an older, slower-changing inflammation marker. Neither test tells you where the inflammation is — your doctor interprets them with symptoms.

CRP is one of the most useful and widely ordered blood tests. It rises quickly — within 6–8 hours of an inflammatory trigger — and falls quickly as the problem resolves, which makes it good for tracking whether an infection is responding to treatment.

What Raises CRP?

Infections

• Bacterial infections typically raise CRP more than viral ones
• Pneumonia, urinary infections, abscesses, sepsis

Inflammatory and Autoimmune Conditions

• Rheumatoid arthritis and other inflammatory arthritis — see joint pain tests
• Inflammatory bowel disease
• Vasculitis

Other Causes

• Injury, surgery and burns
• Obesity — fat tissue produces inflammatory signals
• Smoking
• Poor sleep and chronic stress (mild rises)
• Some cancers

CRP vs hs-CRP

• Standard CRP: detects moderate to high levels — used for infection and inflammation
• hs-CRP: detects very low levels — used for cardiovascular risk assessment in people who are otherwise well

hs-CRP and Heart Risk

• Below 1 mg/L: lower risk
• 1–3 mg/L: average risk
• Above 3 mg/L: higher risk

hs-CRP should be measured when you are well — not during a cold or after an injury — and is often repeated to confirm. It adds to, but doesn't replace, cholesterol, sugar and BP. See heart attacks in young Indians and lipid profile.

CRP vs ESR

• CRP rises and falls within hours to days — good for acute monitoring
• ESR changes over days to weeks — affected by anaemia, age, pregnancy and protein levels
• Both are non-specific
• Doctors often order both, especially for joint problems and suspected autoimmune conditions

When Doctors Order a CRP Test

• Fever, to help distinguish bacterial from viral causes (with other tests) — see fever panel
• Monitoring response to antibiotics
• Suspected or known inflammatory arthritis or bowel disease
• After surgery, to watch for complications
• Unexplained fatigue, weight loss or aches
• Heart risk assessment (hs-CRP)

What If My CRP Is High?

• Mildly raised with no symptoms: may reflect a recent minor infection, obesity, smoking or poor sleep — your doctor may repeat it
• Moderately to markedly raised with symptoms: your doctor will look for the cause with examination and further tests
• Persistently raised: may need investigation for chronic inflammatory conditions

How to Prepare

• No fasting needed for CRP alone
• For hs-CRP, test when you've been well for at least two weeks
• Tell the lab about recent infections, injuries, vaccination or surgery
• Avoid intense exercise for 24 hours

Lowering Chronic Inflammation

• Regular exercise
• Weight loss if overweight
• Stopping smoking
• A diet rich in vegetables, fruits, whole grains, nuts and fish; fewer processed foods and sugars
• Good sleep and stress management

Frequently Asked Questions

What is a normal CRP level?

A standard CRP below about 5–10 mg/L, depending on the laboratory, is generally considered normal.

What does a high CRP mean?

High CRP indicates inflammation or infection somewhere in the body. It does not show the location or cause, which your doctor determines with other findings.

What is the difference between CRP and hs-CRP?

Standard CRP detects infection and inflammation. hs-CRP measures very low levels and is used to assess cardiovascular risk.

Is fasting needed for a CRP test?

No. Fasting is not required for a CRP test.

Is CRP better than ESR?

CRP responds faster to changes in inflammation, while ESR changes more slowly. Doctors often use both together.

How long does a CRP report take at Aarvak?

CRP results are usually available the same day, typically within 6–8 hours.

Book a CRP Test in Gurugram

Book CRP, hs-CRP or ESR at our Sector 67 lab or with home sample collection. Call +91 92663 33711. See our immunology tests.

This article is for general information only. Please consult your doctor for interpretation of results.