I am a physician and administer 0.9% NaCl in water ("normal saline") to patients frequently. The bag says it has a pH of 5.5 (compared to the human body of 7.4).

I am asking why the pH is so low. It is because NaCl is the salt of HCl? I read on wikipedia that the pH of NaCl aqueous solutions is 7. I teach medical students and want to give an understandable explanation why the pH on a bag of "normal saline" reads pH 5.5 and when we give lots of saline to patients, they develop acidosis in the blood.

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    $\begingroup$ There is an entire article dedicated to this topic, actually:) $\endgroup$
    – andselisk
    Commented Jan 3, 2018 at 22:39
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    $\begingroup$ Wow. Thank you for the super fast replies!!! That is awesome. I will go through the article you linked and see what it has to say. Much appreciated. $\endgroup$
    – Jason
    Commented Jan 3, 2018 at 22:45
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    $\begingroup$ It would seem that a normal saline solution isn't buffered at pH 5.5. Thus there is really very little acid in an absolute sense. A typical carbonated beverage would have thousands of times more acid. $\endgroup$
    – MaxW
    Commented Jan 3, 2018 at 23:33
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    $\begingroup$ Check this article: ncbi.nlm.nih.gov/pmc/articles/PMC3638298 Saline (0.9% salt solution) seems to be a beast to measure its pH, but harmless to the patients. $\endgroup$
    – user91823
    Commented Apr 7, 2020 at 14:58
  • $\begingroup$ The problem with acidic saline is the activation of bone resorption pathway to release calcium to normalize the blood pH to 7.4, putting old patients at risk of bone fracturs in cases at which high volume of acidic saline is administered. $\endgroup$
    – F Saad
    Commented Jan 11 at 14:31

1 Answer 1


Medical saline has a $\mathrm{pH}$ of 5.5 do to the dissolved $\ce{CO2}$ within the solution as well as factoring in the degradation of the PVC packaging.

I reference the attached article from the International Journal of Medical Sciences from 2013:

Benjamin AJ Reddi, “Why Is Saline So Acidic (and Does It Really Matter?),” Int. J. Med. Sci. 2013, 10(6), 747-750 (doi:10.7150/ijms.5868)(PDF).


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