Can running or a marathon damage the kidneys?
Yes .. but usually, not.
For most healthy people, running — even a marathon — does not cause lasting kidney damage. The kidneys may be stressed during very long or intense exercise, but they normally recover within a day or two.
However, acute kidney injury (AKI) can occur – and in rare situations this can be serious. Extremely rarely, short-term dialysis is required.
Do kidney problems happen with all levels of running?
No. The occasional gentle run – e.g. 1-2 km at slower pace – will have no effect on the kidneys.
Problems occur if you run:
- Long distances
- In the heat
- If you have not trained enough
Why the kidneys are stressed during long runs
During prolonged or intense exercise:
- Blood is redirected to muscles and skin
- Less blood temporarily flows to the kidneys
- Fluid is lost through sweating
This combination can reduce how well the kidneys filter blood for a short time.
Here are common ways running can affect the kidneys.
1. Dehydration (most common)
If you lose more fluid than you replace:
- Blood flow to the kidneys drops
- Kidney function temporarily worsens
This usually improves quickly with rest and drinking fluids.
How can it be diagnosed? If blood tests are done (it is rarely necessary) they will show temporary rises in blood levels of sodium, urea and creatinine. The latter two tests (which are markers of kidney function) will rarely go up more than 50% of baseline levels.
2. Muscle breakdown (rhabdomyolysis; rare but serious) causing acute kidney injury (AKI)
Very intense or unaccustomed exercise can damage muscle tissue, releasing substances into the bloodstream that:
- Can clog and irritate the kidneys
- May cause dark-coloured urine and muscle pain (and tenderness)
This condition is uncommon, but it is the most dangerous kidney-related risk from extreme exercise.
How can it be diagnosed? As well as significant rises in sodium, urea and creatinine (the latter two tests may increase by a factor of 2-3x), there will be rises in potassium, urate and phosphate.
The blood creatine kinase (CK; a muscle enzyme) level will rise – and it is this test that makes the final diagnosis. CK is normally 40–320 IU/L for men and 25–200 IU/L for women.
In rhabdomyolysis it can rise to the 1000s, and occasionally, 10,000s.
What usually happens? AKI can come on quite rapidly (on the day of the race, or the following day). Hospital admission is usually required. Most cases get better with fluid replacement and cooling.
In a few cases, temporary dialysis (usually for less than 10 days) may be required. The kidneys almost always recover – and no long term damage is done.
3. Heat stress (and high sodium levels)
Running in hot or humid conditions:
- Increases dehydration
- Increases core temperature
- Places extra strain on organs, including the kidneys
This risk rises if someone is not heat-acclimatised.
How is this diagnosed? In most cases, it does not need to be diagnosed. In a few cases, there may be mild confusion (due to high sodium levels causing brain shrinkage). This usually reverses with rehydration and cooling.
In a few cases, core temperature and blood sodium levels rise significantly, and hospital admission will be required for IV fluids and cooling.
If this is not done, eventually brain shrinkage and hyperthermia will cause drowsiness (then coma) and fitting (seizures).
4. Blood or protein in the urine
After long runs, some people notice:
- A small amount of blood or protein in urine
- The blood may show itself as dark-coloured urine
But, for some, especially after long distances, quite alot of fresh red blood can be seen. This is called march haematuria.
This is usually harmless and temporary, disappearing within 1–3 days.
5. Painkillers (NSAIDs) increase risk
Taking common painkillers like aspirin, ibuprofen or naproxen before or during long runs:
- Reduces the kidneys’ ability to protect themselves
- Significantly increases the risk of acute kidney injury, especially if dehydrated
This is a major preventable risk.
Does marathon running cause long-term kidney disease?
There is no good evidence that it does in healthy people.
- Short-term kidney changes are common after marathons
- Permanent damage is rare
- Repeated severe episodes (especially with dehydration or painkiller use) may increase risk, but this is uncommon
How to protect your kidneys when running
- Stay well hydrated, but don’t overdo fluids
- Avoid NSAID painkillers (like ibuprofen) before and during long runs
- Build up training gradually
- Be cautious in hot conditions
- Seek medical help if you have:
- Dark urine
- Severe muscle pain
- Little or no urine
- Symptoms lasting more than 48 hours
Bottom Line
Running is generally good for general (and therefore kidney) health.
Why? It will lower weight, reduce likelihood of diabetes, lower blood pressure and cholesterol etc – all of which is good for kidneys.
Marathons can temporarily stress the kidneys, but lasting damage is rare and usually preventable with good hydration, sensible training, and avoiding certain painkillers.
