Urinalysis

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Urine pH

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Urine pH
foto de Fernando Martínez Sáez
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Fernando Martínez Sáez
Medically reviewed by our Medical staff

Last update: 28-06-2021

How else can it be called?

  • Urinary pH

  • Alkaline urine

  • Acidic urine

  • CIE-10: R82.99

What is the urine pH?

The urine pH is a measure to know if the urine is acidic or alkaline. The abbreviation pH stands for “parts hydrogen” or “power of hydrogen” and it is a value based on the concentration of hydrogen ions present on a substance.

A urine pH of 7 is said to be a neutral pH. If the urine pH is above 7 the urine is called alkaline urine, while if the urine pH is below 7 is called acidic urine.

The lungs and the exchange of ions in the urinary tubules of the kidneys primarily control the pH of the human body.

Why is the urine pH test performed?

Urine pH test is an important screening test for the diagnosis of renal disease, respiratory disease, and certain metabolic disorders.

The normal urine pH of a healthy person is an acidic urine (pH between 5.0 and 6.0) if the sample is collected in the morning. If the sample is collected after a meal, the pH values are slightly higher.

The urine pH is important to prevent the formation of kidney stones. For that matter, it is interesting to study the types of crystals that appear in the urine of a patient. Some types of crystals are more likely to form in the presence of acidic urine and other in the presence of alkaline urine.

Sometimes it is convenient to maintain the urine at a certain pH to avoid the formation of certain kidney stones and sometimes the urine is forced to remain acidic or alkaline.

For example, if a patient has a tendency to form uric acid or cystine stones, it may be desirable to keep the urine alkaline or the pH at least as high as 6.5. Sometimes medication is given to achieve an alkaline urine (ammonium chloride, methionine, mandelic acid).

In other situations, it may be desirable that the urine pH remains strongly acid (about 5.5):

  • To prevent the growth of certain bacteria associated with chronic urinary tract infections
  • To prevent the formation of calcium phosphate renal stones in susceptible people

Increasing the acidity of the urine may help prevent both infections and calcium stones. These people can lower the pH of their urine by drinking cranberry juice frequently.

How is the test performed?

This test is performed along with other urine tests in what is called a urinalysis. The patient must collect a sample of the urine in a specific container using a special kit. This sample will be sent to the lab for the analysis.

The pH test is measured frequently using reagent strips or dipsticks. The dipstick may comprise a reagent or chemical pad. It reacts, show a different color depending on the pH, when it is dipped into the urine specimen.

In laboratories, there are automated machines that perform the analysis, but it is also possible to buy strips that let you analyze a urine sample at home. They comprise up to 10 or more different reagents or chemical pads to perform different urine tests at the same time.

Which are considered normal results?

The normal range for pH in the urine is considered to be between 4.5 and 8.

There are different types of urine depending on the pH:

  • pH between 6.5 and 7.5: Neutral urine
  • pH between 6 and 6.5: Acidic urine
  • pH < 5: Very acidic urine
  • pH > 7.5: Alkaline urine

The most often case is a slightly acidic urine with values close to 6.

Very acidic urine
4.555.55.75
Acidic urine
66.5  
Neutral Urine
6.7577.25 
Alkaline urine
7.588.59

There may be also slight differences in the values depending on the laboratory or the procedures used.

Alkaline urine

If the pH is above 7.5, the urine is alkaline. Alkaline urine may be due to:

  • Vegetarian diet or a high intake of citrus fruits or vegetables
  • Urinary tract infection by bacteria, such as proteus, pseudomonas, etc. (except Escherichia Coli)
  • Respiratory alkalosis (hyperventilation)
  • Vomiting
  • Renal tubular acidosis
  • Chronic renal failure

Acidic urine

If the pH is below 6.5, the urine is acidic. Acidic urine may be due to:

  • High protein diet with high intake of meat and eggs
  • Cranberry juice intake
  • Metabolic acidosis
  • Respiratory acidosis
  • Diabetic ketoacidosis
  • Emphysema
  • Mellitus diabetes
  • Starvation
  • Dehydration
  • Severe diarrhea
  • Uremia
  • Escherichia Coli infection

Which substance or process may interfere with the results?

Some drugs used to treat urinary tract infections, such as mandelamine (methamine mandelate) or fosfomycin trometamol, may contribute to become the urine more acidic (pH<7).

Some treatments using sulfonamides or drugs used for the treatment of kidney stones with bicarbonate, potassium citrate or acetazolamide may contribute to become the urine more alkaline (pH>7).

Medically reviewed by our Medical staff on 28-06-2021

Bibliography

  • Laboratory tests and diagnostic procedures with nursing diagnoses (8th ed), Jane Vincent Corbett, Angela Denise Banks, ISBN: 978-0-13-237332-6, Pag. 63
  • Essentials of Medical Laboratory Practice. Constance L. Lieseke, Elizabeth A. Zeibig. 2012. ISBN: 978-0-8036-1899-2 Pag: 419.

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