Average Amount of Stomach Acid in the Human Stomach

Your stomach secretes a variety of fluids that aid in digestion, including stomach acid. Stomach acid is composed primarily of hydrochloric acid, making the stomach a very acidic environment with a pH of 1 to 2. The body closely regulates the production and secretion of stomach acid, since too much or too little has adverse effects on your digestive and overall health.

A doctor is explaining test results to her patient. (Image: javi_indy/iStock/Getty Images)

Functions

At the onset of eating, G cells present in the stomach, duodenum and pancreas release a hormone called gastrin. Gastrin then stimulates parietal cells in the stomach to produce and secrete stomach acid and other fluids. Stomach acid activates digestive enzymes, denatures large protein molecules for easier digestion and kills ingested microorganisms, such as bacteria. The duodenum secretes large quantities of sodium bicarbonate as highly acidic stomach contents move into the small intestine. This helps neutralize the pH to prevent damage to the other digestive organs.

Stomach Acid Test and Average Levels

Your physician will use a stomach acid test to measure the amount and pH of your stomach acid. The content of fluid in your stomach should average between 20 and 100mL with a pH of 1.5 to 3.5, according to MedlinePlus.

Hypochlorhydria

Hypochlorhydria and achlorhydria refer to the production of little or no stomach acid. The absence of stomach acid has several complications since it aids in food digestion. Without stomach acid, proteins move into the small intestine intact and too big for the body to absorb. This can lead to protein malabsorption and malnutrition, according to Dr. Sarah Myhill. The absorption of vitamin B-12 also depends on sufficient stomach acid. Mild vitamin B-12 deficiency can lead to depression, fatigue and poor memory; prolonged deficiency can cause irreversible brain and nerve damage. Lastly, the absence of stomach acid can lead to infections caused by ingested microorganisms.

Hyperchlorhydria

Hyperchlorhydria is the condition of too much acid in the stomach fluid. It can also refer to stomach acid with a pH that is too low. Mucous cells along the stomach lumen secrete mucus to prevent stomach acid from reaching and damaging the stomach wall, which can cause sores called peptic ulcers. Peptic ulcers are characterized by burning stomach pain that worsens after eating. Spicy foods, stress, alcohol and smoking exacerbate ulcer symptoms.