Urine is made up of water, salts, and waste products from the kidneys. The balance of these compounds can affect 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 other diagnostic tests when a person has symptoms possibly related to a problem in the urinary tract or kidneys.

The common value for urine pH is 6.0–7.5 for most people, but any value within the 4.5–8.0 range is generally not a cause for concern. The pH scale runs from 1 to 14, with 1 being the most acidic and 14 the most basic.

However, 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 a person eats. A doctor may ask a person about their typical nutrition before evaluating their urine pH results, as that may affect the “normal” results for that person.

There’s some research that diets high in animal protein and cereal grains are more acidic while diets high in fruits and vegetables are more alkaline, or basic.

Acidic foods include:

  • grains
  • sodas
  • animal-protein foods
  • sugary foods

Alkaline foods include:

  • nuts
  • vegetables
  • most fruits

A doctor will assess a person’s urine pH according to the reason for doing the urinalysis. Urine pH that falls outside of the expected range can be a sign of an infection, a problem with kidney function, or it can be a sign that therapy to change the urine pH is working.

Many factors affect urine pH, and it can vary greatly, so a doctor cannot diagnose a medical condition based on pH alone. For instance, a high pH could signal a urinary tract infection (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.

Carbonic anhydrase inhibitor medications, such as acetazolamide (Diamox) aim to make urine more alkaline, so a doctor may take more than one sample to see whether the pH is changing.

Typically a urine pH test does not require special preparation. However, a doctor may ask a person to fast beforehand if the urinalysis includes other tests in addition to pH. If a person does not need to fast, they may still need to avoid foods that can change the color of their urine.

A doctor may also ask about medications or supplements a person is taking, as they can interfere with the test results.

Sometimes a doctor will want a person to continue taking these medications to determine a person’s urine pH while they are taking them. However, a doctor might ask someone to stop taking those drugs or supplements before the test.

A doctor may ask for a one-time urine sample, or a 24-hour urine test, where a person collects their urine several times over the course of one day.

A person will collect a one-time urine sample using the “clean-catch” method to prevent bacteria from entering the sample by catching the urine midstream. This method requires a person to clean their genital area, release a small amount of urine, and collect about 2 ounces (oz) or 60 milliliters (ml) of urine for pH testing.

Both one-time samples and 24-hour urine samples undergo urinalysis.

A urinalysis has three major components:

  • Physical, 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.
  • Chemical dipstick test: A dipstick test involves holding a piece of specially treated paper called 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 normally to provide the sample, although the doctor may ask for the first urine of the day or a midstream sample. For a 24-hour sample, they may offer additional instructions, such as fully emptying the bladder at the beginning of the collection day.

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.

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 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.

Is a high urine pH dangerous?

High urine pH is not dangerous in and of itself. However, it can be a sign of a condition that may need treatment, such as UTIs or some types of kidney stones.

What does a high pH in urine mean?

High urine pH means the urine is alkaline, or basic with a pH between 7–14. A doctor will assess high pH along with other indicators to determine if someone has an infection or other medical condition.

What causes elevated pH in urine?

A UTI and kidney stones are two possible causes of an elevated pH, but there are others. Certain medications can also increase urine pH, such as acetazolamide (Diamox).