All information on pH-value

At a glance

The pH value indicates whether an aqueous solution is acidic, neutral, or basic.

It is indicated on a scale from 0 to 14. A pH of 7 is called neutral.

If the pH is less than 7, the analyzed liquid is acidic. Above 7, the pH value is alkaline or basic.

Conceptually, the letter abbreviation “pH” derives from the Latin ‘potentia Hydrogenii’ (potentia = force; hydrogenium = hydrogen). It is a measure of the content of H+ ions (more precisely: H3O ions) in a solution.

The pH value is calculated on the basis of the amount of positively charged hydrogen ions present in the liquid.

Further information

The pH in the urine of a healthy person is slightly acidic on average (normal range 4.8 to 7.6). Due to food intake and various metabolic processes, the pH value fluctuates during the day.

Since human urine fluctuates around pH 6.5, in clinical language use, urine is sometimes

  • pH below 6.5 than more acidic (azidottic) and
  • pH above 6.5 than more alkaline

even if this is not chemically correct.


If a patient is given a decrease in pH, it is called an acidosis, with an increase of an alkalosis.

However, there are areas in the body where there is a permanently acidic climate, e.g. in the stomach (pH 1 – 2) or on the skin (pH 5.5).


pH values in the body

  • Gastric juice: 1.2-3.0
  • Saliva: about 7.0
  • Lebergalle: about 7.1
  • Pancreatic secretion: about 8.0
  • Urine: 5.6-7.0


The pH of the blood is 7.4. A person can only survive a few minutes if his blood pH drops to 7.0 or rises to 7.8. Under normal conditions, so-called buffer systems of the blood prevent such pH fluctuations. These make it possible to neutralize excess acids with basic substances or even excess bases with an acid.


Division of buffer systems in the blood:

  • Phosphate buffer: 5%
  • Protein buffer: 7%
  • Hemoglobin Buffer: 35%
  • Hydrogen carbonate buffer: 53%


In addition, excess acids are excreted via the kidneys as components of the urine as well as component of the breathing. CO2 generally accumulates as a metabolic end product in all cells. This gas is physically dissolved in the blood as carbonic acid. In order to remove the carbonic acid from the body, we exhale CO2 through the lungs.

Various conclusions can be drawn about the state of health from the pH value in the urine.

If it is e.B. above 8 and nitrite is also found in the urine, the cause can be a bacterial infection of the urinary tract.

Metabolic status as well as various diseases and medications also affect pH.


Possible causes of a highly acidic urine in the longer term are:


Diagnostic significance:

Persistently high or low values may indicate a disturbed acid-base balance.

Permanently alkaline (high) levels occur in some bacterial urinary tract infections.

A latent acidosis (acidification) of the body can best be detected by a measurement of the pH value. It should be noted that a single measurement is not meaningful due to the high fluctuation width. It should be measured and logged about 5 times a day on at least 5 days (possibly always at about the same time). If the pH value is permanently too low, for example, a healthy diet can counteract it.


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  • Roche Diagnostics Deutschland GmbH (2014): Kompendium der Urinanalyse. Urinteststreifen und Mikroskopie, 1-196
  • Schroeder, U. (02/2017), Übersäuerung – basische Ernährung– Entschlackung, Tritime
  • Westphalen von, G.: Säure-Basen-Haushalt, URL:äure-Basen-Haushalt, Retrieved 18.06.2019
  • Lahnsteiner, E. et al. (2004): Harnanalyse – praktisch zusammengefasst, 2. Auflage
Status of information: Spring 2020