Arthritis Blood Tests Explained: CRP, ESR, Rheumatoid Factor, Anti-CCP and More

Name: Arthritis Blood Tests Explained: CRP, RF, Anti-CCP (UK)
Creator: Louis Maxwell

Written by Louis Maxwell — First Contact Practitioner, HCPC PH128483.

Written by the Living With Arthritis team · pending clinical review by Louis Maxwell (HCPC PH128483)

Quick answer: Blood tests support, but rarely prove, a diagnosis of inflammatory arthritis. CRP and ESR measure inflammation; rheumatoid factor and anti-CCP antibodies point towards rheumatoid arthritis; HLA-B27 helps assess axial spondyloarthritis; urate helps diagnose and treat gout. Osteoarthritis has no blood test. Medicines such as methotrexate need regular blood count, liver and kidney checks.

Checked on 10 October 2026 against the NHS guide to blood tests, NHS pages on diagnosing rheumatoid arthritis, ankylosing spondylitis and polymyalgia rheumatica, NHS methotrexate guidance, and NICE guidelines NG100, NG65 and NG219.

Blood tests are part of almost every arthritis journey: to help find out what is causing joint symptoms, to check how active a condition is, and to keep medicines safe. But results are easy to misread. A positive test does not always mean you have a condition, and a normal test does not always rule one out. This guide explains the common tests, what they can and cannot tell you, and what to do with your results.

The key point: no single blood test diagnoses most arthritis

The NHS says no blood test can definitively prove or rule out rheumatoid arthritis. The same is true for most types of inflammatory arthritis. Doctors combine your symptoms, the examination, blood tests and sometimes scans such as X-rays or MRI. Osteoarthritis has no blood test at all; NICE says it is diagnosed clinically.

NICE also says blood tests ordered in primary care should not delay referral to rheumatology for someone with suspected persistent synovitis (joint inflammation). If your joints are swollen, a normal blood test does not mean you should not be referred.

Tests for inflammation: CRP and ESR

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are general markers of inflammation. The NHS lists both as main blood tests used when rheumatoid arthritis is suspected.

They can be raised in inflammatory arthritis, polymyalgia rheumatica and many other conditions, including infections.
They can be normal even when a joint is inflamed, particularly in psoriatic arthritis and axial spondyloarthritis.
For polymyalgia rheumatica, the NHS says that if both ESR and CRP are normal, PMR is unlikely. Sometimes ESR is normal and CRP is raised, which is why both are usually done.
Rheumatology teams use CRP to monitor how active a condition is. For adults with active rheumatoid arthritis, NICE recommends measuring CRP and a disease activity score monthly in specialist care until the treatment target is reached.

A raised result does not tell you where the inflammation is or what is causing it.

Antibody tests for rheumatoid arthritis

Rheumatoid factor (RF)

NICE recommends offering a rheumatoid factor test to adults with suspected rheumatoid arthritis who have synovitis on examination. The NHS explains that more than half of people with rheumatoid arthritis have high levels of rheumatoid factor when the disease starts, but about 1 in 20 people without rheumatoid arthritis also test positive. So a positive RF is a clue, not a diagnosis, and a negative RF does not rule it out.

Anti-CCP antibodies

NICE says to consider measuring anti-CCP antibodies if rheumatoid factor is negative, and to measure them at diagnosis if not done already. The NHS says people who test positive for anti-CCP are very likely to develop rheumatoid arthritis, but not everyone with rheumatoid arthritis has this antibody. People who test positive for both RF and anti-CCP may be more likely to have more severe disease, which can affect how intensively it is treated.

NICE is clear that urgent referral is still needed for suspected persistent synovitis even if RF or anti-CCP is negative.

HLA-B27 for axial spondyloarthritis

HLA-B27 is a genetic marker, tested with a blood sample. The NHS explains it is found in most people with ankylosing spondylitis, but not everyone with the condition has it, and some people have it without ever developing the condition. NICE's guideline uses HLA-B27 as part of deciding whether someone with long-standing back pain that started before age 45 should be referred for a spondyloarthritis assessment.

Urate for gout

NICE recommends measuring serum urate in people with symptoms and signs of gout. A level of 360 micromol/litre or more supports the diagnosis. Urate can fall during a flare, so if it is below this during a flare and gout is still strongly suspected, NICE says to repeat it at least 2 weeks after the flare has settled.

If you take urate-lowering treatment such as allopurinol, NICE recommends a treat-to-target approach: monthly urate checks to guide dose increases until you reach a target below 360 micromol/litre, or below 300 for some people with tophi or frequent flares.

Other tests you may have

Full blood count (FBC): checks red cells, white cells and platelets. The NHS notes anaemia is common in rheumatoid arthritis, although anaemia does not prove you have it. FBC is also key for monitoring medicines.
Kidney function (urea and electrolytes, eGFR): important before and during many arthritis medicines, and for gout.
Liver function tests (LFTs): used to monitor medicines such as methotrexate and leflunomide.
Antinuclear antibodies (ANA) and related tests: used when a connective tissue disease such as lupus is suspected. The NHS says lupus may be diagnosed if tests show high levels of a certain type of antibody together with typical symptoms. ANA is also positive in many healthy people, so it is interpreted with your symptoms.
Thyroid tests, vitamin D, calcium and glucose: may be used to look for other causes of aches, fatigue or bone problems.
Infection screening (for example hepatitis B and C, HIV and tuberculosis tests) before starting some immune-suppressing or biologic medicines.

Monitoring blood tests when you take arthritis medicines

Many disease-modifying medicines can affect your blood count, liver or kidneys, so regular blood tests are part of taking them safely. For methotrexate, for example, the NHS says that when you first start, you will have a check-up and blood tests to check your blood, liver and kidneys every 1 to 2 weeks. Once the dose is right and your treatment is working, this usually becomes every 2 to 3 months. You will usually be given a booklet to record your dose and results.

Once you are stable, the hospital may ask your GP to continue prescribing and monitoring under a shared care arrangement. Check who is responsible for booking your tests and acting on the results.

Tips for monitoring tests:

Put your test dates in your calendar and set reminders.
Keep your monitoring booklet or app up to date and bring it to appointments.
If you are going on holiday, plan your test around it rather than missing it.
Never carry on taking a medicine that needs monitoring if you have missed several tests. Contact your team.
Ask what results would mean a change in your dose, and who will contact you if one is abnormal.

See our guide to leflunomide blood tests and side effects for an example of a monitoring schedule, and starting a new arthritis medicine for questions to ask.

Having a blood test

The NHS explains that blood tests are usually done at a GP surgery or hospital and take about 10 minutes. Blood is usually taken from the inside of your elbow with a needle. Some surgeries and hospitals let you book online.

Check whether you need to fast. Most arthritis tests do not need fasting, but cholesterol or glucose tests sometimes do.
Drink water beforehand unless told not to; it can make veins easier to find.
Wear a top with sleeves that roll up easily.
If you are worried about needles, tell the person taking blood. You can bring someone with you.
If your hands or arms are painful or swollen, say which arm is better.

You may get some bruising, which should go away in a few days.

Getting and understanding your results

The NHS says you may get results after a few days, and usually within a few weeks. Some GP surgeries only contact you if they need to discuss them. You may be able to see results in the NHS App or your NHS account.

When you look at results yourself:

Reference ranges vary between laboratories. Results are shown alongside the normal range for that lab.
A result just outside the range is often not significant. Normal ranges are based on most healthy people, so some healthy people fall slightly outside them.
Trends matter more than single results. Your team will look at how results change over time.
Results need context. A positive antibody without symptoms may mean nothing; a normal CRP with swollen joints still needs assessment.

If you do not hear anything after a few weeks, or you do not understand a result, contact your GP surgery or specialist team. If you are waiting for a rheumatology appointment, take copies or a list of recent results with you; our guide to what happens at a rheumatology appointment explains what to bring.

Why tests are sometimes repeated

Being asked for another sample does not necessarily mean something is wrong. Common reasons include:

a borderline result that needs checking, because many results vary from day to day
a sample that clotted, was too small or was delayed getting to the laboratory
timing, such as repeating a urate level after a gout flare has settled, as NICE recommends
checking a trend, for example whether inflammation markers are falling after starting treatment
a new medicine that needs a baseline before you start

Questions to ask about your results

Which results were outside the normal range, and do they matter for me?
Do they change my diagnosis or treatment?
Do I need any further tests, and when?
Who will contact me if a monitoring result means I need to change or stop a medicine?
Can I have a copy, or see them in the NHS App?

Blood tests while you wait for rheumatology

Your GP may arrange tests such as CRP, ESR, full blood count, rheumatoid factor, anti-CCP or urate before or after referring you. These can help the rheumatology team prioritise your referral, but NICE is clear they should not delay it. If your symptoms change while you wait, for example more joints become swollen, tell your GP: repeat tests and an updated referral letter may help. Our waiting list guide explains what else you can do.

Quick reference

Test	Mainly used for	Remember
CRP, ESR	Inflammation, disease activity, PMR	Not specific; can be normal in inflamed joints
Rheumatoid factor	Suspected rheumatoid arthritis	About 1 in 20 people without RA test positive
Anti-CCP	Suspected rheumatoid arthritis, prognosis	Not everyone with RA has it
HLA-B27	Suspected axial spondyloarthritis	Many people with HLA-B27 never develop it
Serum urate	Gout diagnosis and treatment target	Can fall during a flare
FBC, liver, kidney tests	General health and medicine monitoring	Regular checks with many DMARDs

When to get medical help

Same day: if you take methotrexate, leflunomide, sulfasalazine, a biologic or another immune-suppressing medicine and develop a fever, sore throat, mouth ulcers, unexplained bruising or bleeding, yellowing of the skin or eyes, or a new cough or breathlessness. Contact your rheumatology advice line, GP or NHS 111.
Urgently: a hot, swollen, very painful joint, especially with fever. Get an urgent GP appointment or contact NHS 111.
Soon: if you have been told a result is abnormal and nobody has explained the next step.
999: severe breathlessness, chest pain or collapse.

Frequently asked questions

Can a blood test show if I have arthritis?

Blood tests can support a diagnosis of some types of inflammatory arthritis and gout, but no single test proves or rules out most types. Osteoarthritis does not show on blood tests.

My rheumatoid factor is positive. Do I have rheumatoid arthritis?

Not necessarily. The NHS says about 1 in 20 people without rheumatoid arthritis test positive. Diagnosis depends on symptoms and examination as well as tests.

My blood tests are normal but my joints are swollen. What now?

Normal tests do not rule out inflammatory arthritis. NICE says referral for suspected persistent synovitis should not be delayed by test results, and should be urgent even if inflammatory markers or antibodies are normal.

Do I need to fast before an arthritis blood test?

Usually not, but some tests, such as cholesterol or glucose, may need fasting. You will be told if you need to.

How often will I need blood tests on methotrexate?

The NHS says every 1 to 2 weeks when you start, and usually every 2 to 3 months once you are stable. Your team will confirm your schedule.

Can I see my results online?

You may be able to see them in the NHS App or your NHS account. Ask your GP surgery or team to explain anything you do not understand.

Sources and further reading

Educational information for people in the United Kingdom, not personal medical, legal or financial advice. NHS processes, rules and prices change, so check the linked official sources and speak to your GP, specialist team or pharmacist about your own situation. Charity no. 1218461. Pending clinical review. If you feel very unwell, call 999 or go to A&E. For urgent advice, contact NHS 111.

Continue with related help

How arthritis is diagnosed — tests, scans and results
X-rays explained — what they show
MRI scans explained — when they help
What happens at a rheumatology appointment — your first visit

Last updated 2026-10-10. This is general information, not a substitute for personalised medical advice.