Urine comprises water, salts, and waste products from the kidneys. The balance of these compounds can affect the urine's acidity levels, which specialists measure in pH.
The pH is the measurement of how acidic or alkaline a person's urine is. Doctors often test the urine pH, and they may perform other diagnostic tests, when a person has symptoms that may be related to a problem in the urinary tract.
According to the American Association for Clinical Chemistry, the average value for urine pH is 6.0, but it can range from 4.5 to 8.0. Urine under 5.0 is acidic, and urine higher than 8.0 is alkaline, or basic.
Different laboratories may have different ranges for "normal" pH levels. The laboratory report will explain the normal and abnormal levels for the specific laboratory. A doctor will usually explain these results to the person.
One of the major factors affecting urine pH is the food that a person eats. A doctor will likely ask a person about the foods they typically eat before evaluating their urine pH results.
Acidic foods include:
- high-protein foods
- sugary foods
Alkaline foods include:
- most fruits
If a person has a high urine pH, meaning that it is more alkaline, it might signal a medical condition such as:
A person can also have a higher urine pH due to prolonged vomiting. This rids the body of stomach acid, which can make body fluids more basic.
Acidic urine can also create an environment where kidney stones can form.
If a person has low urine pH, meaning that it is more acidic, it might indicate a medical condition such as:
Taking certain medications can also make a person's urine pH more basic or acidic.
A person should ask their doctor if they should stop taking certain medications the night or morning of a urinalysis. However, sometimes a doctor will want a person to continue taking these medications to determine a person's urine pH while they are taking them.
Because many factors affect urine pH, and because it can vary greatly, a doctor cannot diagnose a medical condition based on pH alone. For instance, a pH of over 7 could signal a UTI or a different kind of infection.
A doctor may consider urine pH along with other symptoms to make a diagnosis. They may also order a urine pH test to study the effectiveness of kidney stone treatments.
Medications such as carbonic anhydrase inhibitors (acetazolamide) aim to make urine more alkaline, so a doctor may take more than one sample to see whether the pH is changing.
Sometimes, a doctor may ask for a "clean-catch" urine sample to prevent bacteria from entering the sample. This means that a person will clean their genital area, release a small amount of urine, and collect 1–2 ounces of urine for pH testing.
A urinalysis has three major components:
- Visual exam: When a doctor or laboratory technician examines the urine, they will look at its color, whether foreign material such as blood is present in the urine, and whether the urine appears foamy.
- Dipstick test: A dipstick test involves holding a piece of specially treated paper, or litmus paper, in a urine sample. The dipstick will change color to show how acidic or alkaline the urine is. It may also change color if other substances, such as glucose, white blood cells, bilirubin, or proteins, are present in the urine.
- Microscopic exam: A laboratory technician will examine a small amount of urine under a microscope to look for particles, such as red blood cells, crystals, or white blood cells. These are not usually present in the urine and can indicate an underlying medical condition.
A urine pH test does not cause side effects. A person will urinate as they normally would to provide the sample.
The acidity or alkalinity of urine can help a doctor diagnose medical conditions. Doctors can test urine pH using a litmus paper test.
A doctor can perform a urine pH test as part of a larger urinalysis test, or a they can specifically test urine pH.
High and low pH levels can indicate problems with a person's kidneys, such as an environment that could help kidney stones develop.