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What Is the pH of Stomach Acid?

By Nancy Drummond ; Updated July 27, 2017

Stomach acid, also known as gastric acid, is the primary digestive agent in the body. Dr. Ronen Arai, writing for, says stomach acid is designed “to help break down foods and aid digestion.” Consequently, stomach acid is most effective in digestion when it has a low pH level, making it highly acidic. Incorrect pH and abnormal levels of stomach acid can lead to medical complications, including acid reflux, ulcers and gastritis (stomach inflammation).

The Facts

The American Heritage Dictionary defines pH as “a measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14.” Simply put, solutions with low pH are highly acidic. The normal pH range for stomach acid is between 1.5 and 3.5, making it highly acidic. This acidity creates an ideal environment for pepsin, the main digestive enzyme, to break down food.


Nurse practitioner Marcelle Pick, on the website, says the stomach wall has five layers, including mucosa, submucosa and layers of muscle. The innermost layer, the mucosa, manufactures stomach acid and pepsin. The acid is comprised mainly of hydrochloric acid (HCl). Normal stomach acid volume ranges from 20 to 100 mL, or about 1 tablespoon to just under half a cup.


The pH of stomach acid is important in maintaining healthy digestion. A pH that is too low can lead to ulcerative conditions, while an abnormally high pH prevents proper food breakdown. A study at the University of Michigan Medical School also confirmed that reduced stomach acidity can make the stomach more susceptible to bacterial infections that can cause ulcers and gastritis.


Stomach acid pH levels can be affected by infection, stress and other physiological phenomena. High acidity (low pH) can lead to upset stomach and feelings of indigestion, but—contrary to popular belief—specific food choices have little to do with stomach acid pH. Gloria Tsang, a registered dietician for, points out that drinking milk to calm an acidic stomach can help temporarily but may result in overproduction of acid later.


The best way to maintain a proper stomach acid pH level is through behavioral measures. Gloria Tsang, R.D., says, “Only two behavioral changes can reduce symptoms of acid stomach—eating less and elevating your head while sleeping.” Marcelle Pick, NP, adds that reducing stress and maintaining good posture can also help preserve the proper stomach acid pH balance.

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