Stomach acid is hydrochloric acid at a pH of 1, which means that it is at a concentration of 0.1 moles/liter. When something is swallowed, it reaches the stomach within seconds.

You can have your stomach acid level tested - the test measures the quantity and acidity of stomach contents.

After a period of fasting, fluid is all that remains in the stomach. This fluid can be removed via a tube inserted through the esophagus (food pipe).

To test the ability of cells in the stomach to secrete acid, gastrin may be injected just under the skin, into a muscle, or into a vein. The stomach contents are then removed and analyzed.

Another test involves insulin-induced hypoglycemia. Enough insulin is given under the skin or through a vein to cause the blood sugar to decrease. This causes the vagus nerve to stimulate the release of gastrin. After a short time, the stomach contents are removed and analyzed.

How to Prepare for the Test

You will be asked not to eat or drink for four to six hours before the test.

How the Test Will Feel

You may notice some discomfort or a gagging feeling as the tube is passed through your nose or mouth, and down your esophagus.

Why the Test is Performed

This test may be used for a number of reasons:

To test for the cause of ulcers
To check if material is coming back up from the small intestine
To evaluate the cause of malabsorption
To check if anti-ulcer medications work
To test the secretion of gastrin

Normal Results

Normally the volume of the stomach fluid is 20 to 100 mL and the pH is acidic (1.5 to 3.5).

What Abnormal Results Mean

Ulcers may be caused by delayed emptying or increased secretion of acid.
The presence of bile in the stomach indicates backing up of material from the duodenum. This may occur after a partial gastrectomy. (See also gastroesophageal reflux disease).
Decreased levels of stomach acid or gastrin can cause malabsorption (not enough absorption of nutrients from the intestines).
Increased levels of gastrin may cause increased secretion of acid and may lead to ulcers (Zollinger-Ellison syndrome).

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