Rhabdomyolysis: Warning signs and kidney risks

Some soreness is normal after a new workout or a physically demanding day. But severe muscle pain, unusual weakness or dark urine (pee) may signal rhabdomyolysis, a condition that requires immediate medical attention. 

Here is an overview of the condition to help you avoid this serious situation, including how it can affect your kidneys and warning signs to look out for.

What is rhabdomyolysis?

Rhabdomyolysis, or "rhabdo," occurs when damaged muscle tissue breaks down, releasing substances into the blood called myoglobin.

What causes rhabdomyolysis?

Intense exercise — especially beyond your usual level — can cause rhabdo. Extreme heat, severe dehydration, muscle injuries, certain illnesses and some medicines or substances can also contribute to this. Anyone can develop it, not just athletes.

How does rhabdo affect your kidneys?

As your kidneys filter it, myoglobin can harm kidney cells and cause acute kidney injury (AKI), which is a sudden decline in kidney function. Dehydration can worsen the damage by reducing blood flow to the kidneys. The kidneys may struggle to remove waste and extra fluid or balance minerals. You may make less urine, but you can still have an acute kidney injury even when urine output seems normal.

Muscle breakdown also releases potassium into the blood causing hyperkalemia (elevated levels of potassium in the blood). If your kidneys cannot clear the excess potassium, it can build up and cause dangerous heart rhythm changes.

What are the warning signs of rhabdo?

Symptoms may happen hours or days after a muscle injury and can include:

• Muscle pain or cramps that are worse than expected
• Unusual weakness or trouble with daily activities
• Dark, tea- or cola-colored urine
• Passing less urine than usual

You may not have every one of these symptoms. Seek help without waiting for your urine to change color.

What steps should you take?

If you suspect rhabdo, stop what you are doing and get medical care immediately. Do not let drinking water or resting delay medical care.

Tell your healthcare team about recent strenuous activity, heat exposure, injuries, illnesses and any medicines or supplements you take. Blood tests can detect muscle damage and check your kidney function and electrolytes, including potassium levels. You may need repeat tests to track changes for improvement or worsening.

How is rhabdo treated?

The treatment of rhabdo depends on how much muscle has broken down and how your body has been affected. You may need intravenous (IV) fluids and monitoring during a hospital stay. If severe, you may need temporary dialysis to remove waste and extra fluid while the kidneys recover.

Not everyone with rhabdo develops AKI. Early care can lower the risk of serious complications. Follow your healthcare team's advice on repeat blood tests and when to resume work or exercise. Once you are cleared by a healthcare professional, you can build up activity gradually and should take breaks when working or exercising.