There’s no single blood test that proves PMR. Doctors look at the pattern: your story and exam plus inflammation tests (ESR/CRP). Other tests help rule out look-alike problems and set a safe baseline before treatment. A small group of people with clear PMR can have near-normal inflammatory markers — so your whole picture matters.
This guide explains every blood test you’ll likely see — what it measures, what “abnormal” means in PMR, how often to repeat it, and where labs can mislead.
The core inflammation tests
C-reactive protein (CRP)
- What it is: A fast-moving marker of inflammation made by the liver.
- Units: Usually mg/L (sometimes mg/dL; multiply mg/dL ×10 to convert to mg/L).
- PMR pattern: Often elevated at diagnosis; with effective prednisone, CRP typically falls quickly (days to 1–3 weeks).
- Why it’s useful: Tracks today’s disease activity well and changes promptly when you flare or improve.
- Caveats: Infections, injuries, and other conditions also raise CRP. People on IL-6 inhibitors (e.g., tocilizumab, sarilumab) may have falsely low/normal CRP even with active disease or infection.
Erythrocyte sedimentation rate (ESR)
- What it is: A slower, indirect inflammation marker.
- Units: mm/hour.
- PMR pattern: Frequently elevated at diagnosis; sometimes remains higher than CRP later in disease.
- Why it’s useful: Complements CRP; in some cohorts, a higher ESR correlates with relapse risk.
- Caveats: Influenced by age, anemia, and proteins in the blood — so it can read high even if inflammation is modest, and occasionally normal when PMR is active.
Bottom line: Most people with PMR start with CRP and ESR both elevated. Your team will usually order both and follow them together with your symptoms.
Baseline “rule-out” and safety labs
These tests help confirm PMR, exclude look-alike conditions, and set a safe starting point for treatment.
Complete blood count (CBC)
- Why: Looks for anemia, elevated platelets (which can rise in inflammation), and white-cell counts (infection or drug effects).
- Clues: Markedly high platelets plus very high CRP/ESR may strengthen concern for giant cell arteritis (GCA) when symptoms fit.
Comprehensive metabolic panel (CMP)
- Why: Checks kidney and liver function, electrolytes, and glucose — important before and during steroids or methotrexate.
- Clues: Elevated glucose is common on prednisone; abnormal liver enzymes affect medicine choice/dose.
Thyroid-stimulating hormone (TSH)
- Why: Low thyroid function can mimic PMR fatigue and stiffness.
Creatine kinase (CK)
- Why: Screens for myopathies (including statin-related) that can masquerade as PMR aches/weakness.
Rheumatoid factor (RF) and anti-CCP antibodies
- Why: Help distinguish PMR from seronegative/elderly-onset rheumatoid arthritis, which can present with shoulder/hip pain and morning stiffness.
Antinuclear antibodies (ANA) ± other immune panels (selective)
- Why: Considered when symptoms suggest polymyositis, lupus, vasculitis, or other connective-tissue diseases.
When GCA is on the table (urgent)
Because up to ~1 in 5 people with PMR may develop giant cell arteritis, your clinician will watch for new headache, scalp tenderness, jaw pain with chewing, or visual symptoms. Labs alone can’t rule GCA in or out, but very high CRP/ESR plus those symptoms raise suspicion. Further vascular imaging (and sometimes biopsy) is urgent; treatment escalates immediately.
Do not wait for blood results if visual symptoms appear—seek care at once.
Labs that monitor medicines (and why timing matters)
While on glucocorticoids (prednisone/prednisolone)
- Track: CRP/ESR (response/relapse), glucose/A1c, blood pressure, weight, sometimes lipids.
- Why: Steroids can raise blood sugar, BP, and lipids and increase infection risk. Many teams also check vitamin D and assess calcium intake/needs.
If you start methotrexate (steroid-sparing)
- Before starting: CBC, liver enzymes (AST/ALT), albumin, creatinine/eGFR, and screening for hepatitis B/C (± HIV/TB if risk factors).
- After starting or dose changes: Labs every 2 weeks for ~6 weeks, then monthly for 3–12 months, then every 2–3 months when stable (CBC, LFTs, creatinine/eGFR).
- Why: Watch for bone-marrow suppression, liver irritation, or kidney issues; folic acid reduces side effects without blunting benefit.
If you use an IL-6 inhibitor (tocilizumab, sarilumab)
- Expect: CRP/ESR suppression regardless of symptoms—your team will rely more on how you feel, exam, and other labs.
- Monitor: CBC (neutropenia), LFTs, and lipids (IL-6 blockade can raise cholesterol). Report fever/infection symptoms early, because CRP may not “warn” you.
How often are labs repeated?
A common, practical cadence (your clinician will individualize):
- Diagnosis/early treatment (first 2–4 weeks): CRP/ESR to confirm response; CBC/CMP as baseline.
- Taper phase (first 3–6 months): Visits every 4–8 weeks with CRP/ESR; safety checks depending on medicines and risk.
- Stable phase: Every 2–3 months (or wider) for CRP/ESR, plus medication-specific safety labs on schedule.
- Any relapse symptoms: Repeat CRP/ESR and re-examine; adjust dose if labs and symptoms agree (and even if they don’t, if the clinical picture is convincing).
Interpreting results (without getting tripped up)
- Trends beat single numbers. A CRP of 18 mg/L dropping to 6 mg/L means more than any one result.
- Symptoms matter most. Labs are decision support, not the decision. If you’re stiff and sore again, your team won’t ignore that because the CRP is “only slightly up.”
- Normal labs don’t fully exclude PMR. A small minority have normal CRP/ESR at diagnosis; imaging and a careful response-to-treatment assessment help in these cases.
- Not all high CRP/ESR is PMR. Infections, new illnesses, and even obesity can raise results—your clinician will consider context.
- Drug effects can mask signals. IL-6 inhibitors flatten CRP/ESR; steroids may partially normalize labs while symptoms are still settling.
A simple checklist for your next blood draw
☐ Are we checking both CRP and ESR?
☐ Do I need CBC/CMP now (based on my medicines)?
☐ If I’m on methotrexate, is my folic acid plan clear and labs on schedule?
☐ If I’m on an IL-6 inhibitor, do I know the plan for lipids/CBC/LFTs and when to call for infection symptoms?
☐ Have I told the team about new headaches, jaw pain, or visual changes (possible GCA)?
Frequently asked questions
What numbers are “normal”?
Reference ranges vary by lab. Many use CRP <10 mg/L and ESR <20–30 mm/h in older adults. Your report lists the local range.
How quickly should CRP/ESR fall after starting steroids?
Symptoms often improve within days; CRP/ESR generally decline over 1–3 weeks. Persistently high numbers prompt a re-check of dose, adherence, infections, or alternative diagnoses.
My CRP is normal but I feel worse—now what?
Relapses can be clinical. Your clinician may still adjust treatment and consider ultrasound or other tests. CRP/ESR are helpful, not infallible.
Can diet or stress change my labs?
Major shifts come from disease activity and medication. That said, poor sleep, acute stress, infections, and metabolic issues can nudge CRP upward. Focus on steady routines and report intercurrent illness.
Bottom line
For PMR, blood tests are guides, not verdicts. CRP + ESR anchor diagnosis and monitoring, while CBC/CMP and targeted panels keep treatment safe and rule out mimics. During therapy, lab timing depends on your medicines and symptoms. Track trends, tell your team about red-flag symptoms (especially possible GCA), and use labs to support—not replace—good clinical decisions.
Medical disclaimer: Educational content only. Always follow the plan you and your clinician set together.
Does having taken naproxen for pain symptoms interfere with the CRP and ESR labs?
My labs were negative, but I’d been taking naproxen for pain.