Why Is There Blood in Urine After Running?

Every long distance runner should keep an eye on their urine output. Urine output gives a good idea about fluid balance of the body and it is extremely important to monitor it if the weather is too hot. Marathon runners and athletes are familiar with the fact that the urine can be very concentrated when they urinate after a long session of running or training. Sometimes there can be a little bit of blood in it.


The presence of blood in urine after running can be due to many reasons, some of them are:

1.      Impact on the Walls of the Bladder

The scientific term used for blood in urine is hematuria. The most common cause of hematuria after running is impact on the bladder walls. The bladder walls contain a lot of very delicate blood vessels. During running, especially with an empty bladder, there is impact on the bladder walls. The repeated impact of force on bladder walls while running can be sufficient to damage the blood vessels and this injury can lead to bleeding. If you have noticed some blood in your urine after a prolonged running session, try to avoid emptying your bladder before the session. When some amount of urine is present in the urinary bladder during running, the chances of injury are reduced.

The extent of internal injury can be viewed with the help of a cystoscope and it can take a few days to heal completely.

2.      Altered Permeability of the Filtering Apparatus

Another reason of blood in urine after running can be altered permeability of the glomeruli. The kidneys are made up of thousands of microscopic filters or glomeruli. In normal circumstances the membranes of these do not allow blood to pass through. However, after running or strenuous exercise the permeability of these can increase, allowing some red blood cells to pass along with filtered urine. This can lead to hematuria. This condition is temporary and gets resolved after the exercise is stopped.

3.      Increased Fragility of Red Blood Cells

The red color of blood is due to the presence of hemoglobin. In normal circumstances hemoglobin is contained within red blood cells. If the red blood cells get damaged due to some reason hemoglobin is released in the blood. This hemoglobin can get filtered through the kidneys and can give red discoloration to the urine. Some people have more fragile red blood cells than others and their red cells can get damaged during running due to increased fragility. This phenomenon is known as hemoglobinuria or foot strike haemolysis.

4.      Other Causes

Running is not the sole cause of hematuria. The presence of blood in urine after running can be due to many other reasons. If you notice blood in your urine you should seek medical advice for correct diagnosis and treatment. Some common causes are:

  • UTI or Urinary Tract Infection: A very common cause of microscopic hematuria in older age group is infection of the urinary tract. The bacteria can enter the urinary tract through the urethra and start multiplying. The symptoms can be burning or pain while passing urine, very foul smelling urine or a constant urge to urinate.
  • Kidney Stones: Kidney stones or bladder stones can cause hematuria. These stones are formed when certain minerals are concentrated and crystallized in kidneys or in the bladder wall. With the passage of time these small crystals can become bigger stones. They can remain silent for a long time. If they cause obstruction of the urinary tract they can lead to severe pain or bleeding which is noted as the presence of blood in urine.
  • Enlarged Prostate Gland: The prostate gland is located at the base of urinary bladder and it encircles the top most part or urethra in males. If it gets enlarged it can compress the urethra and urination becomes difficult. Other signs of an enlarged prostate are a persistent urge to pass urine and the presence of blood in urine. Infection of the prostate gland can also lead to similar symptoms.
  • Kidney Diseases: The inflammation of the filtration system or glomerulonephritis often leads to hematuria. Glomerulonephritis can either be a part of systemic disease or can only affect the kidneys. It can happen after a streptococcal sore throat.
  • Cancer: The presence of frank blood in urine can be a sign of cancer of the kidneys, prostate or bladder. It happens in the advanced stage and there are usually no other signs at early stages.
  • Hereditary Disorders: People with certain hereditary disorders are likely to have hematuria. These disorders include sickle cell anemia where the red cells can get damaged easily and Alport syndrome which affects the filtration system of the kidneys.
  • Injury: Any injury to the kidneys can cause hematuria. If you get a blow on your kidneys you can notice some blood in your urine.
  • Medications: Certain medicines like chemotherapy medicine cyclophosphamide and blood thinners are likely to cause hematuria.

Any Way to Prevent It?

There is no absolute way to prevent hematuria after running. However, there are certain things you can do if you notice blood in urine after running. These preventive measures include keeping yourself well hydrated and running with a partially full bladder. If you notice some blood in urine after strenuous exercise and there are no accompanying symptoms you don't need to worry about it.

When to Worry

The presence of blood in urine after running is not uncommon, but do get yourself checked by a doctor if you notice it. If there is accompanying backache or fever, you might have an infection which needs to be treated.