Influenza-induced rhabdomyolysis: what to know

Muscle cells release substances into the blood when they are damaged. A clinician may check your symptoms, hydration, blood tests and urine to assess the muscle injury and protect kidney function.

Rhabdomyolysis can occur during a viral illness, including influenza, although other triggers such as intense exertion, injury, heat exposure or certain medicines may also be involved. Muscle pain, marked weakness, tenderness, swelling or unusually dark urine can occur. Fever and reduced fluid intake may add to dehydration, which can make the situation more concerning. The illness itself may cause body aches, but severe or worsening muscle symptoms deserve a separate assessment.

Contact a healthcare service promptly if influenza is accompanied by severe muscle pain, weakness, difficulty walking or dark urine. Do not resume strenuous exercise while you are unwell. Follow the clinician’s advice about fluids, prescribed medicines and repeat blood or urine testing. Tell them about medicines, supplements, recent exercise, vomiting and any change in how often you urinate. Rest is sensible, but it does not replace assessment when muscle breakdown is suspected.

Seek urgent care for dark brown or tea-coloured urine, very little urine, rapidly increasing muscle swelling, severe weakness, faintness, confusion, chest symptoms or trouble breathing. These signs can accompany significant muscle injury, dehydration or complications that need immediate treatment. Call emergency services if you cannot stay awake, are struggling to breathe or feel severely unwell.

Ask which tests are needed to measure muscle injury and kidney function, whether any medicine or exercise could have contributed, how much activity is appropriate during recovery, and which urine or weakness changes should trigger a return visit.