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What Lab Tests Look for Blood in the Urine?

written by: Dr Mike C•edited by: Emma Lloyd•updated: 5/18/2010

Lab tests for blood in urine usually just involve dipping a test strip into a fresh urine sample. The condition of having blood present in your urine is called hematuria, but the amount of blood may be too low to be seen with the naked eye. The condition may be trivial but can also signal a problem.

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    Blood In Urine - What Does It Mean?

    Normally, when a healthy person urinates they will not see any traces of blood in their urine. Although it is alarming to see blood in the urine, it is not necessarily sinister as it can be caused by vigorous exercise or taking certain common medications, such as Aspirin. However, the cause could be more serious and should be established if the condition lasts more than a few days.

    The clinical term for the condition of passing blood in your urine is called hematuria. Hematuria is divided into two groups, the second of which is called microscopic hematuria in which the quantity of blood, though present in the urine, is such that it can only be seen with the aid of a microscope (or detected via sensitive lab tests for blood in urine).

    Hematuria will be seen as a red, pink or even “cola" colour in urine and the changed colour is caused by the presence of erythrocytes (red blood cells) in the urine. The depth of the colour will depend upon the extent of the bleeding and also the concentration of the urine (this in turn depends upon how much fluid has been drunk and the interval between urination). The condition itself is normally painless (unless a blood clot is being passed).

    There are certain foods that can change the colour of urine. These include rhubarb, berries and beets. The laxative Ex-lax, is also known to alter the colour of urine, and certain medications may also affect its colour. It is worth thinking of these benign causes before consulting a doctor; if they are the cause, the problem will usually clear a day after their consumption has ceased.

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    Causes Of Blood In The Urine

    Blood in the urine can be associated with a number of underlying conditions which could need to be treated – indeed, some of these conditions are potentially life-threatening.

    The most likely cause of hematuria is an infection in the urinary tract due to the presence of bacteria in the bladder. If the infection spreads, it can cause an infection in the kidneys, although the initial source of a bacteriological kidney infection may also be blood borne. Bacteriological infections can usually be treated effectively with a course of antibiotics.

    Other forms of kidney disease (e.g. diabetes, immune disease or viral infection) may also cause blood to be seen in the urine. Physical damage to the kidneys through accident or contact sports, such as boxing, may also cause blood to appear in the urine.

    Bladder and kidney stones may both lead to the presence of blood in the urine due to the physical damage they can cause in the affected organ.

    Inherited conditions such as Alport syndrome and sickle cell anaemia can also cause the symptoms of hematuria. Inflammation of the prostate may also lead to hematuria.

    Cancer in the bladder, prostate or kidneys may also cause the presence of blood in urine; however, this usually will only occur once the cancer has become quite advanced and more difficult to treat.

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    Testing For Blood In Urine

    Gross hematuria is so obvious that a lab test for blood in urine is unnecessary other than to confirm the visual diagnosis. However, the underlying cause of any blood in the urine will need to be ascertained. The presence of blood in urine can be confirmed by using a test strip which is dipped into the urine; often such a test may diagnose a range of other conditions on the same test stick at the same time. The test stick will undergo a colour change which can be used for diagnostic purposes.

    There is a number of different parameters that can be utilised to detect the presence of blood in urine on these sticks (such as enzymatic activity of peroxidase or glucose) which provide the basis for the colour change in response to a chemical reaction. These test strips require no specialist facilities and can be used and interpreted at your doctor's office or in a health clinic.

    The presence of red or white blood cells in a droplet of a urine sample can be determined under a microscope. This technique can be used to check for hematuria in a urine sample which is not obviously coloured.

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    1. The Mayo Clinic:
    2. Merck:
    3. Urine Test website: