Gastrin is the major hormone that regulates acid secretion in the stomach. It is produced by special cells in the stomach. Small amounts of gastrin may also be produced by the pancreas and possibly the intestines. When there is food in the stomach, gastrin is released into the blood. As stomach and intestinal acidity rises, gastrin production normally decreases.

A laboratory test can be done to measure the amount of gastrin in the blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

Drugs that can increase gastrin measurements include antacids, H2-blocking agents (such as cimetidine), and proton pump inhibitors (such as omeprazole).

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Your doctor may order this test if you have signs or symptoms of a disorder associated with abnormal gastrin production.

Normal values are generally less than 100 pg/ml (picograms per milliliter).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Too much gastrin causes severe peptic ulcer disease. Greater-than-normal levels may also be due to:

• Chronic atrophic gastritis
• G-cell hyperplasia (overactivity of gastrin-producing cells in the stomach)
• use of antacids or other acid-suppressive medications
• Zollinger-Ellison syndrome, a gastrin-producing tumor that may develop in the stomach or pancreas

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)