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C-reactive protein (CRP) by nephelometry

Published: August 9, 2026Updated: August 16, 2026

This blood test measures the level of C-reactive protein, a substance produced by your liver in response to inflammation or infection.

Quick summary

["CRP helps track inflammation in your body."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
101118-8
Short code
SEZFC
Synonyms
Bld Doc FC
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) tube, ACD (yellow-top) tube, or sodium heparin (green-top) tube; sterile tube acceptable if processed within 24 hours
Units
N/A
Ref low
0
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
88184 (flow cytometry, cell surface, cytoplasmic, or nuclear marker, technical component only - first marker); 88185 (each additional marker); 88187 (interpretation, 2-8 markers); 88188 (interpretation, 9-15 markers); 88189 (interpretation, 16 or more markers)
SNOMED
427276002
Specimen volume
3-5 mL of whole blood; minimum 1 mL for pediatric samples
Stability
EDTA: ambient temperature 24-48 hours; refrigerated (2-8°C) up to 72 hours; do not freeze. ACD: ambient up to 48 hours; refrigerated up to 72 hours. Specimen should be processed within 24-48 hours of collection for optimal viability.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test to check for signs of inflammation, monitor conditions like arthritis, heart disease, or infections, or evaluate responses to treatments. It can also help assess risk for certain diseases, such as cardiovascular issues.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a broader lipid panel, but this is not always required for CRP alone. Bring any medications you’re currently taking to your appointment.

How the Test Works

A small blood sample is drawn from a vein in your arm. The blood is sent to a lab where it’s analyzed using nephelometry, a method that measures how much light scatters when CRP binds to antibodies. The result indicates the concentration of CRP in your blood.

What the Results Mean

CRP levels vary depending on your health status. Higher than normal levels may signal inflammation, infection, or other underlying conditions. Your provider will interpret results in the context of your medical history and symptoms.

Reference range

Negative for Sézary syndrome. Atypical Sézary cell count <1.0 x 10^9/L or <1000 cells/µL. CD4:CD8 ratio <4:1 (normal range). CD4+/CD7- and CD4+/CD26- populations should be <30% of total lymphocytes. Results interpreted in conjunction with morphology, clinical findings, and molecular studies (T-cell receptor gene rearrangement).N/A

Specimen: whole-blood

No special preparation required. Patient should be informed that peripheral blood sample is needed. Clinical correlation with skin biopsy findings is recommended. Avoid recent corticosteroid therapy if possible, as it may affect lymphocyte subset populations.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated CRP is often an early marker of inflammation, which can occur with infections (like pneumonia or urinary tract infections), autoimmune diseases (like rheumatoid arthritis), or chronic conditions (like heart disease or certain cancers). It’s also used to monitor treatment effectiveness or disease progression. Low or normal levels generally suggest minimal inflammation, but further evaluation may be needed if symptoms persist.

Short name

CRP (Nephelometry)

Frequently asked questions

How long does it take to get CRP test results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will contact you with the final report once it’s ready.
Can CRP levels change with diet or exercise?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Reducing inflammation through healthy eating, regular physical activity, and avoiding smoking may help lower CRP over time. Always discuss lifestyle changes with your provider before making significant adjustments.
Is CRP the same as a white blood cell count (WBC) test?
No, CRP and WBC are different. CRP specifically measures a protein linked to inflammation, while WBC counts the number of white blood cells in your blood. Both tests can be used together to assess immune response, but they provide distinct information.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy