Blood tests commonly ordered for joint pain
| Test | Normal Range | What it checks for |
|---|---|---|
| Uric Acid (men) | 3.5–7.2 mg/dL | Gout — crystals depositing in joints |
| Uric Acid (women) | 2.6–6.0 mg/dL | Gout (less common in women before menopause) |
| CRP (C-reactive protein) | < 10 mg/L | Active inflammation — rises fast |
| ESR | Men: <15 mm/hr; Women: <20 mm/hr | Ongoing inflammation or infection |
| Rheumatoid Factor (RF) | < 14 IU/mL | Rheumatoid arthritis marker |
| Anti-CCP antibodies | Negative / <20 U/mL | More specific for rheumatoid arthritis than RF |
| ANA (Antinuclear Antibodies) | Negative / <1:40 | Lupus and other autoimmune joint diseases |
| Calcium | 8.5–10.5 mg/dL | Calcium pyrophosphate crystal disease (pseudogout) |
What causes joint pain?
Gout — uric acid crystals
Gout causes sudden, severe joint pain — most often in the big toe, ankle or knee. High uric acid levels lead to crystal deposits in joints. Gout attacks are intensely painful and cause redness, swelling and warmth. Blood uric acid above 7.2 mg/dL (men) or 6.0 mg/dL (women) increases the risk of gout, though levels can be normal during an acute attack.
Rheumatoid Arthritis — autoimmune
RA is an autoimmune disease where the immune system attacks joint linings (synovium). It typically affects small joints of hands and feet symmetrically, causes morning stiffness lasting over an hour, and progresses to joint damage if untreated. Positive RF and Anti-CCP antibodies support the diagnosis. ESR and CRP indicate disease activity.
Osteoarthritis — wear and tear
Osteoarthritis is mechanical wear of cartilage, most common in knees, hips and spine. It tends to worsen through the day (unlike RA which is worse in the morning). Blood tests are usually normal — diagnosis is mainly clinical and confirmed on X-ray showing joint space narrowing.
Lupus (SLE) — systemic autoimmune
Systemic lupus erythematosus commonly causes joint pain and swelling along with a butterfly-shaped facial rash, fatigue, kidney problems and sun sensitivity. ANA is positive in about 95% of lupus cases, but is not specific — it can be positive in other conditions too. Further tests (anti-dsDNA, anti-Sm) help confirm lupus.
Reactive arthritis and infection
Joints can become inflamed after infections — particularly intestinal or urinary infections (reactive arthritis). Viral infections like dengue, chikungunya and parvovirus B19 cause significant joint pain. Blood cultures, viral serology and joint fluid analysis may be needed. ESR and CRP will typically be elevated.
What does a high CRP with joint pain mean?
A high CRP indicates active inflammation. Combined with joint pain, it suggests an inflammatory arthritis (RA, gout, infection) rather than mechanical wear and tear (osteoarthritis). CRP normalises quickly with effective treatment, making it useful for monitoring response to therapy. A normal CRP with joint pain points more towards osteoarthritis, fibromyalgia, or mechanical causes.
What does a positive Rheumatoid Factor mean?
Rheumatoid Factor (RF) is not perfectly specific for rheumatoid arthritis. About 70–80% of people with RA have positive RF, but RF can also be positive in other conditions including lupus, Sjögren's syndrome, hepatitis C, and even in 5% of healthy individuals. A positive RF alone is not enough to diagnose RA. Anti-CCP antibodies are more specific — being positive in about 95% of RA cases and rarely positive without RA.
Questions to ask your doctor
- Do I need anti-CCP antibodies and ANA tests?
- Should I see a rheumatologist?
- Is my joint pain gout, RA, or something else?
- Do I need X-rays or an MRI of the affected joints?
- What can I do for pain relief while waiting for test results?