Blood in urine can be common for athletes who overexert themselves during physical activity. The medical term is Hematuria. This happened to me almost two years ago from lifting too heavy, too soon, when I decided to get back into shape. I took some antibiotics for three days and it cleared it right up. Also, drink plenty of cranberry juice and water, no sodas.
Here is one definition I found on Hematuria:
Overview
Hematuria is the presence of blood, specifically red blood cells, in the urine. Whether the blood is visible only under a microscope or visible to the naked eye, hematuria is a sign that something is causing bleeding in the genitourinary tract: the kidneys, the tubes that carry urine from the kidneys to the bladder (ureters), the prostate gland (in men), the bladder, or the tube that carries urine from the bladder out of the body (urethra).
Bleeding may happen once or it may be recurrent. It can indicate different problems in men and women. Causes of this condition range from non–life threatening (e.g., urinary tract infection) to serious (e.g., cancer, kidney disease). Therefore, a physician should be consulted as soon as possible.
Types
There are two types of hematuria, microscopic and gross (or macroscopic). In microscopic hematuria, the amount of blood in the urine is so small that it can be seen only under a microscope. A small number of people experience microscopic hematuria that has no discernible cause (idiopathic hematuria). These people normally excrete a higher number of red blood cells.
In gross hematuria the urine is pink, red, or dark brown and may contain small blood clots. The amount of blood in the urine does not necessarily indicate the seriousness of the underlying problem. As little as 1 milliliter (0.03 ounces) of blood will turn the urine red.
"Joggers hematuria" results from repeated jarring of the bladder during jogging or long-distance running.
Reddish urine that is not caused by blood in the urine is called pseudohematuria. Excessive consumption of beets, berries, or rhubarb; food coloring; and certain laxatives and pain medications can produce pink or reddish urine.
Incidence
Hematuria occurs in up to 10% of the general population.
Causes
Many conditions are associated with hematuria. The most common causes include the following:
Benign prostatic hyperplasia (BPH) in men over 40
Kidney and bladder stones
Kidney disease
Medications (e.g., quinine, rifampin, phenytoin)
Trauma (e.g., a blow to the kidneys)
Tumors and/or cancer in the urinary system
Urinary tract blockages
Viral infections of the urinary tract and sexually transmitted diseases, particularly in women
There are rare diseases and genetic disorders that also cause hematuria. Some of these are:
Sickle cell anemia (inherited blood disorder)
Systemic lupus erythmatosus (chronic inflammatory disorder of connective tissue)
von Hippel-Landau disease (hereditary disease in which benign tumors form on the spinal cord, kidneys, testicles, and other organs)
Signs and Symptoms
In many cases, blood in the urine (gross or microscopic) is the only sign of a disorder. In others, a variety of symptoms, such as the following, may be present.
Abdominal pain
Decreased urinary force, hesitance, incomplete voiding
Fever
Frequent urination (polyuria)
Pain during urination (dysuria)
Pain in the flank or side
