Blood-coloured urine and rhabdomyolysis: what to know

Rhabdomyolysis is rapid breakdown of muscle tissue. Damaged cells release myoglobin, which can make urine look cola-coloured, brown or red. This may be mistaken for blood, but urine microscopy can show few red blood cells. Triggers include unusually intense exercise, heat illness, a crush injury, prolonged pressure on a muscle, seizures and some medicines or substances. Muscle tenderness, swelling, weakness and reduced urine can occur. The kidneys remove myoglobin, and a large load can interfere with their filtering work.

Stop the activity that preceded the symptoms and arrange urgent medical assessment, particularly after heat exposure, injury or prolonged immobility. A clinician may measure muscle enzymes, electrolytes and kidney function, and examine a urine sample. Treatment is chosen according to the findings and may include monitored fluids. Do not exercise through weakness or take unapproved anti-inflammatory medicines to mask pain. Share every prescription, supplement and recreational substance with the clinician.

Go to an emergency department for dark urine with severe muscle pain or weakness, reduced or absent urine, increasing swelling, confusion, fainting, chest symptoms, abnormal heartbeat or persistent vomiting. Emergency review is also needed after a major crush injury or heat illness. Symptoms can worsen even when the initial muscle soreness seems manageable, so do not wait for the urine to become clear.

Could this be myoglobin rather than urinary blood? How are my muscle enzymes and kidney function being checked? Which medicines should I avoid? When can I safely return to exercise? Which urine or swelling changes require immediate help?