Inflammation . Patient guide
C-Reactive Protein (CRP) Blood Test
What is CRP
CRP is a protein made by the liver that rises within hours of an inflammatory stimulus. It is the most widely used general marker of acute or chronic inflammation in UK clinical practice.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in mg/L. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Typical adult range | under 5 | mg/L; varies between labs |
| Mildly raised | 5 to 10 | |
| Moderately raised | 10 to 100 | |
| Significantly raised | over 100 |
What it is
In response to certain cytokines (IL-6 in particular), the liver synthesises CRP. Levels rise within 6 to 12 hours of an inflammatory trigger, peak around 48 hours, and fall as the trigger resolves. CRP is non-specific: it tells you that inflammation is present but not where or why.
Why a clinician would order it
In unexplained fatigue, joint or muscle aches, post-viral recovery monitoring, work-up of autoimmune disease, as part of a pre-treatment baseline, and in pre-operative bloodwork (especially before a hair transplant). A high-sensitivity CRP is sometimes used to estimate longer-term cardiovascular risk in research and private practice, though it is not part of NHS risk tools such as QRISK3 or NICE NG238 lipid pathways.
If your level is outside the range
Symptoms of low CRP
- No symptoms attributable to a low CRP
What low can indicate. Normal background inflammation. A low CRP does not exclude all chronic inflammatory conditions.
Symptoms of high CRP
- Symptoms relate to the underlying cause, e.g. fever, joint pain, fatigue, breathlessness
What high can indicate. Acute infection, chronic inflammation (autoimmune disease), recent surgery or trauma, malignancy, post-viral inflammation. CRP cannot identify the cause on its own; clinical context matters.
Testing tips
No fasting required. CRP can be transiently elevated by recent vigorous exercise or any minor illness, so consider repeating after 4 to 6 weeks if a mildly raised value is unexplained.
If you book C-Reactive Protein as part of Hair Loss Essentials, Advanced Hair & Hormone Check, Pre-Transplant Screening, Pre-Transplant + BBV Screen or General Wellness, the panel needs a fast of at least 12 hours (water is fine), so follow the panel instructions rather than the single-marker advice above.
Where you can get this tested
C-Reactive Protein is included in the following WMG Health panels. Same-day appointments are usually available at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Looking to book a test?
Comprehensive private health screening
Full blood screening at 134 Harley Street, London, reviewed by GMC-registered doctors with a written interpretation.
Symptoms often investigated with C-Reactive Protein
C-Reactive Protein is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about CRP
What is a normal CRP range?
Typical adult range: under 5 (mg/L; varies between labs). Mildly raised: 5 to 10. Moderately raised: 10 to 100. Significantly raised: over 100. Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low CRP result mean?
Normal background inflammation. A low CRP does not exclude all chronic inflammatory conditions.
What does a high CRP result mean?
Acute infection, chronic inflammation (autoimmune disease), recent surgery or trauma, malignancy, post-viral inflammation. CRP cannot identify the cause on its own; clinical context matters.
Do I need to fast or prepare for the CRP blood test?
No fasting required. CRP can be transiently elevated by recent vigorous exercise or any minor illness, so consider repeating after 4 to 6 weeks if a mildly raised value is unexplained. If you book C-Reactive Protein as part of Hair Loss Essentials, Advanced Hair & Hormone Check, Pre-Transplant Screening, Pre-Transplant + BBV Screen or General Wellness, the panel needs a fast of at least 12 hours (water is fine), so follow the panel instructions rather than the single-marker advice above.
Can I order a CRP blood test privately in London?
Yes. WMG Health offers CRP in several standard panels and as part of a custom panel at our 134 Harley Street clinic. Results are released as each marker is reviewed, and the completion date is set by the slowest marker in your panel. We confirm the expected timeframe at booking. Book a standard panel online, or ask for a custom panel via /contact/ or 020 3239 3378.