Test Overview

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:

• Find out why a peptic ulcer keeps coming back.
• Check for certain diseases, such as tumours 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 eat or drink anything with caffeine, such as coffee, 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.

Be sure to tell your doctor about all the non-prescription and prescription medicines you take. Be sure to mention any acid-reducing medicines you take, such as Pepcid (famotidine), Prilosec (omeprazole), or Tums. You may need to stop taking some medicines before this test.

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

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

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

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Results are usually available in 1 to 2 days.

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High levels

High gastrin levels may be caused by:

• Zollinger-Ellison syndrome, a rare disease that can cause gastrin levels to increase as high as 450,000 pg/mL.
• Pernicious anemia and conditions in which the stomach is not able to produce gastric acid, such as atrophic gastritis.
• Kidney failure.
• Diseases such as G-cell hyperplasia, peptic ulcers, hypercalcemia, hyperparathyroidism, sarcoidosis, and stomach cancer.
• Surgery to remove a large portion of the intestines (small bowel resection).

Low levels

Low gastrin levels may be caused by hypothyroidism.