A gastrin test measures the level of the hormone gastrin in the blood. Gastrin is produced by cells called G cells in the stomach lining. When food enters the stomach, G cells trigger the release of gastrin in the blood. As blood levels of gastrin rise, the stomach releases acid (gastric acid) that helps break down and digest food. When enough gastric acid has been produced by the stomach, gastrin levels in the blood drop.

Gastrin also has minor effects on the pancreas, liver, and intestines. Gastrin helps the pancreas produce enzymes for digestion and helps the liver produce bile. It also stimulates the intestines to help move food through the digestive tract.

Sometimes a test for gastrin is done after eating a high-protein diet or after receiving an injection of the digestive hormone secretin into a vein. This is called an intravenous secretin test.

Why It Is Done

A gastrin test may be done to:

• Check for certain diseases, such as tumors of the pancreas or small intestine (Zollinger-Ellison syndrome) or abnormal growth of cells that line the stomach (G-cell hyperplasia).
• Help identify pernicious anemia.

How To Prepare

Before having the gastrin test:

• Do not drink alcohol for 24 hours before the test.
• Do not eat for 12 hours before the test.
• Do not chew gum or smoke cigarettes for 4 hours before the test.
• You can drink as much water as you want up to 1 hour before the test.

Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. You may need to stop taking some medicines before this test. Do not take nonprescription acid-reducing medicines, such as Pepcid, Zantac, Prilosec, Tums, or Rolaids, for 12 hours before the test.

Stress can affect gastrin levels, so you may be asked to rest quietly for 30 minutes before the blood sample is drawn.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?) .

How It Is Done

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure on the site and then put on a bandage.

For a secretin test, a blood sample is drawn and then the digestive hormone secretin is injected into a vein in your arm. Additional blood samples are drawn at the time of the injection, then every 5 minutes until 15 minutes have passed, and then again at 30 minutes after the secretin injection.