CRP Blood Test Explained
What C-reactive protein measures, the Australian normal range, what high CRP really means, and how the test differs from hsCRP — with cost, preparation, and pitfalls.
The Short Answer
CRP (C-reactive protein) is a protein made by your liver in response to inflammation anywhere in your body. The test measures how much CRP is in your blood. In Australia, levels under 5 mg/L are normal. Higher levels mean something is inflamed — an infection, an autoimmune flare, recent surgery, or another cause — but the test does not tell you where the inflammation is. CRP is bulk-billed under Medicare when ordered by your GP for a clinical reason, with private cost typically $30 to $60 if no rebate applies.
What CRP Actually Measures
C-reactive protein is what doctors call an acute-phase reactant. When immune cells encounter infection or tissue damage, they release signalling molecules — primarily interleukin-6 — that travel to the liver. The liver responds by ramping up CRP production within 6 hours. CRP levels can rise from under 1 mg/L to over 100 mg/L in a single day, and they fall just as quickly once the inflammation resolves, usually halving every 18 to 24 hours.
This rapid rise and fall makes CRP one of the most useful inflammatory markers in medicine. Unlike erythrocyte sedimentation rate (ESR), which takes days to change, CRP responds in real time. That is why your GP or emergency department might order serial CRPs to track whether an infection is responding to antibiotics.
Importantly, CRP does not tell you where the inflammation is. It is a sensitive but non-specific marker — like a smoke alarm that tells you there is a fire in the house but not which room. Interpretation always requires clinical context.
Standard CRP vs hsCRP
CRP and high-sensitivity CRP (hsCRP) measure the same protein. The difference is the assay. Standard CRP detects inflammation from about 1 mg/L upward and is used to investigate infection or active disease. hsCRP uses a more sensitive technique that can measure down to about 0.1 mg/L and is used to assess long-term cardiovascular risk in otherwise healthy people.
Standard CRP
Used for acute illness, suspected infection, inflammatory disease monitoring, post-operative checks, and unexplained fever.
Reports values from 1 mg/L upwards
MBS item 65070
hsCRP (high-sensitivity)
Used for cardiovascular risk stratification in apparently healthy adults, often alongside cholesterol and blood pressure.
Reports values from 0.1 mg/L
Often not Medicare-rebated
Normal CRP Ranges in Australia
Australian pathology labs broadly agree on the cutoffs below, although the exact upper limit of normal varies between providers (typically 3, 5, or 8 mg/L). Always read your result against the reference range on your own report.
Under 5 mg/L
Background inflammation only. No active infection or significant inflammatory disease detected. This is the typical level in healthy adults.
5 to 10 mg/L
Low-grade inflammation. May reflect a recent minor infection, modest obesity-related inflammation, smoking, or a flare of a chronic condition. Often repeated in 2 to 4 weeks to see if it settles.
10 to 40 mg/L
Active inflammation, viral infection, autoimmune flare, or early bacterial infection. Your GP will usually look for a clinical cause or order further tests.
40 to 100 mg/L
Substantial inflammation. Common in bacterial infections such as urinary tract infections, pneumonia, cellulitis, or in active inflammatory bowel disease and rheumatoid arthritis.
Over 100 mg/L
Strongly suggests serious bacterial infection, sepsis, abscess, severe trauma, or major tissue damage. Almost always requires urgent medical assessment.
Common Causes of Elevated CRP
Because CRP is non-specific, the list of conditions that can raise it is long. Below are the patterns most commonly seen in Australian general practice and emergency settings.
Bacterial infection
Pneumonia, UTI, cellulitis, abscess, sepsis
Viral infection
Influenza, COVID-19, glandular fever, gastro
Autoimmune disease
Rheumatoid arthritis, lupus, vasculitis flare
Inflammatory bowel disease
Crohn’s disease, ulcerative colitis
Tissue injury
Surgery, trauma, burns, fracture
Chronic low-grade
Obesity, smoking, gum disease, sleep apnoea
Cancer
Active solid tumours, lymphoma
Cardiovascular
Heart attack, unstable angina
Cost — MBS, Medicare and Private Pay
CRP is one of the most commonly ordered tests in Australia and is well covered by Medicare when there is a clinical indication.
MBS item 65070 — C-reactive protein
Bulk-billed at virtually all Sonic (Douglass Hanly Moir, QML, Clinpath), Healius (Laverty, Western Diagnostic, Dorevitch) and Australian Clinical Labs (Health Hub, Mater Pathology) collection centres when ordered by a GP for a relevant indication. You pay nothing out of pocket.
Private (no Medicare rebate)
If you order CRP as part of a self-requested wellness panel through a direct-to-consumer service (e.g. i-screen, MyHealth Lab, OneStop Pathology, Vively), expect to pay $30 to $60 just for the CRP. hsCRP ordered for cardiovascular risk often is not Medicare-rebated and runs $40 to $70.
How to Prepare for a CRP Test
CRP requires almost no preparation. There is no fasting requirement and you can drink water normally. A few practical points:
No fasting needed
CRP is not affected by recent food or drink. If you are also having fasting glucose or a lipid panel, the fast is for those tests, not for CRP.
Skip vigorous exercise the day before
Heavy weights, long runs, HIIT, and competitive sport can transiently raise CRP for 24 to 48 hours. Light walking is fine.
Mention recent infections or vaccines
A cold a week ago or a recent COVID/flu vaccine can leave CRP mildly elevated. Tell the collector and your GP so they can interpret accordingly.
Take medications as usual
Anti-inflammatories (ibuprofen, naproxen) and steroids will lower CRP. Do not stop them, but tell your GP — they may want to know how much suppression to expect.
Pitfalls and Misleading Results
A normal CRP does not rule out disease
CRP can be normal in early infection (it takes 6 to 12 hours to rise), in localised infection without systemic spread, in viral infections that are mild, in some autoimmune conditions like lupus where ESR is more reliable, and in some indolent cancers. Trust your symptoms even if your CRP looks reassuring.
A high CRP does not always mean infection
Obesity, smoking, gum disease, sleep apnoea, the contraceptive pill, hormone replacement therapy, and even chronic stress can keep CRP modestly elevated (typically 3 to 10 mg/L) without an active infection. These are sometimes called “low-grade inflammation” and matter for cardiovascular risk over decades, not for an immediate diagnosis.
Steroids and biologics suppress CRP
If you are on prednisolone, anti-TNF biologics (adalimumab, infliximab), tocilizumab (anti-IL-6, used in rheumatoid arthritis and giant cell arteritis), or other immunosuppressants, your CRP can stay normal even during a serious infection. This is why your rheumatologist or oncologist may rely on other markers and clinical signs.
Single CRP vs trend
A single CRP is a snapshot. Two CRPs 48 hours apart often tell a much better story — falling CRP usually means treatment is working, rising CRP usually means it is not. If your GP recommends a repeat, that is why.
Frequently Asked Questions
What is a normal CRP level in Australia?
In most Australian pathology labs, a CRP under 5 mg/L is considered normal. A standard CRP between 5 and 10 mg/L is mildly elevated, 10 to 100 mg/L suggests significant inflammation or infection, and above 100 mg/L usually indicates serious bacterial infection or major tissue injury.
What is the difference between CRP and hsCRP?
Standard CRP measures inflammation from levels of about 1 mg/L upwards and is used to detect infection or active inflammatory disease. hsCRP (high-sensitivity CRP) uses a more sensitive assay that detects levels as low as 0.1 mg/L and is used to assess long-term cardiovascular risk in otherwise healthy people.
Does Medicare cover the CRP test in Australia?
Yes. CRP is bulk-billed under MBS item 65070 when ordered by your GP for relevant clinical indications such as suspected infection, monitoring of inflammatory disease, or post-operative review. Tests ordered for general wellness checks may not attract a Medicare rebate.
What causes high CRP?
High CRP is caused by anything that triggers inflammation in the body. Common causes include bacterial or viral infections, autoimmune conditions like rheumatoid arthritis or lupus, inflammatory bowel disease, recent surgery, trauma, severe burns, obesity, and active cancers. Even a viral cold can briefly raise CRP.
Do I need to fast for a CRP test?
No. CRP is not affected by recent food intake. You can have a CRP test at any time of day without fasting. However, if your CRP is being measured alongside fasting tests like glucose or a lipid profile, you will need to fast for those.
Can CRP be falsely elevated?
CRP itself is rarely falsely elevated, but it is non-specific. It rises with any inflammation, so a high CRP does not tell you where the inflammation is. Recent vigorous exercise, obesity, oestrogen-containing medications like the contraceptive pill, and pregnancy can all modestly raise baseline CRP.
What does an hsCRP of 3 mg/L mean for heart disease risk?
For cardiovascular risk stratification, hsCRP under 1 mg/L is low risk, 1 to 3 mg/L is intermediate risk, and over 3 mg/L is high risk. An hsCRP of 3 mg/L places you in the upper end of intermediate risk and is worth discussing with your GP alongside your cholesterol and blood pressure.
Related Reading
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This page provides general educational information about the C-reactive protein blood test in Australia. Reference ranges and MBS rules vary and change over time. SmarterBlood does not provide medical advice. Always discuss your individual results with a qualified healthcare professional.