What this test measures
Myoglobin is a small (17 kDa) heme protein in cardiac and skeletal muscle that releases rapidly into blood after muscle injury and is filtered freely by the kidney. Serum myoglobin rises 1–3 hours after MI but is non-specific (any skeletal muscle damage releases it). Urine myoglobin (heme-positive dipstick without red cells) indicates massive muscle breakdown and risk of acute kidney injury from pigment cast nephropathy.
Why it matters
High-sensitivity troponin has replaced myoglobin for MI diagnosis in modern practice. Current main uses: (1) Rhabdomyolysis — sudden weakness, dark urine, very high CK, with raised serum myoglobin and positive urine heme without RBCs; assess risk of AKI. (2) Crush injury and severe trauma. (3) Strenuous-exercise myoglobinuria. (4) Inherited / acquired myopathies. Indian causes include statin myopathy, intense exercise, prolonged immobilisation, snake bite, electrical injury, viral myositis (dengue, influenza), strenuous fasting exercise.
How to prepare
No fasting required. Disclose any recent intense exercise, trauma, immobilisation, statin / fibrate use, recent IM injection, electrical injury, snake bite, and current renal function.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Serum Myoglobin (µg/L (ng/mL))[1][2] | Adults 25 – 75 (assay-dependent) | Low / normal — no significant ongoing muscle injury. | > 75 µg/L: muscle injury. > 500: significant — pursue cause (intense exercise, statin myopathy, viral myositis, crush, snake bite). > 1000: rhabdomyolysis — assess CK (usually > 5× ULN), serum K+ (life-threatening hyperkalaemia), urine output, and start IV fluids; AKI risk rises with peak myoglobin. |
Myoglobin in rhabdomyolysis
| Serum Mb (µg/L) | Likely cause | AKI risk |
|---|---|---|
| < 75 | Normal | None |
| 75 – 500 | Strenuous exercise / minor injury | Low |
| 500 – 5,000 | Moderate myopathy / statin / viral | Possible if dehydrated |
| > 5,000 | Severe rhabdomyolysis / crush | High — admit, IV fluids, monitor K+ |
Frequently asked questions
Is this still used to diagnose heart attacks?
No — modern high-sensitivity troponin has fully replaced myoglobin for MI diagnosis. Myoglobin is too non-specific to be useful as a primary cardiac marker.
My urine is dark red — is it myoglobin?
Possibly. Dark "tea-coloured" urine with positive dipstick blood but no red cells on microscopy points to myoglobin or haemoglobin. Severe muscle pain plus high CK suggests rhabdomyolysis — seek urgent medical care.
Can intense exercise alone raise myoglobin?
Yes — long endurance events (marathons, ultra-running) raise both serum myoglobin and CK; values fall over 24–72 hours. Hydrate well; severe cases can cause AKI.
Will statins affect this test?
Statins occasionally cause myopathy with raised myoglobin and CK. Severe statin-induced rhabdomyolysis is rare but warrants stopping the drug urgently.
How fast does myoglobin clear?
Half-life is short (~2–4 hours) — levels fall quickly once the muscle injury stops. Serial measurements help track ongoing damage.
Related Cardiac Markers tests
Tests commonly ordered alongside MYOGLOBIN, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Myoglobin Test · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Myoglobin, Serum · accessed 2026-05-30T00:00:00.000Z
- ESC 2023 ACS Guidelines · accessed 2026-05-30T00:00:00.000Z
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