Gastrin

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:

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.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A gastrin test measures the level of the hormone gastrin in the blood. Results are usually available in 1 to 2 days.

Normal

The range of normal gastrin values may vary from lab to lab. Normal values may be higher in very young children and older adults.

Gastrin
Adults:

Less than 200 picograms per milliliter (pg/mL) or less than 95 picomoles per liter (pmol/L)

Children:

Less than 125 pg/mL or less than 60 pmol/L

 

Many conditions can change gastrin levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and medical history.

High levels

High gastrin levels may be caused by:

Low levels

Low gastrin levels may be caused by hypothyroidism.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Eating a high-protein food right before the test.
  • Drinking caffeinated beverages or alcohol right before the test.
  • Taking medicines or supplements that contain calcium.
  • Taking medicines that control stomach acid, such as Pepcid, Zantac, or Prilosec.
  • Taking anticholinergic medicines and some medicines used to treat depression (tricyclic antidepressants).
  • Using medicines that contain atropine (such as Motofen or Lomotil).
  • Having abnormally low blood sugar (hypoglycemia).
  • Having had stomach ulcer surgery or a small bowel resection. Increased gastrin levels also occur in medical conditions such as kidney failure, rheumatoid arthritis, and cirrhosis.

What To Think About

  • The level of gastrin in the blood varies throughout the day, but it is usually lowest in the morning.
  • Gastrin test results are most useful when they are evaluated along with medical information gathered from other examinations or tests.
  • If you have normal or mildly elevated gastrin levels but continue to have problems with peptic ulcers, further blood testing may be done. An intravenous secretin test helps determine whether peptic ulcers are being caused by Zollinger-Ellison syndrome. Gastrin levels generally increase by more than 200 picograms per milliliter (pg/mL) in people who have Zollinger-Ellison syndrome, but they rise only slightly or decrease in people who do not have the syndrome.

References

Other Works Consulted

  • Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Handbook of Diagnostic Tests (2003). 3rd ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

Credits

Author Monica Rhodes
Editor Kathleen M. Ariss, MS
Associate Editor Tracy Landauer
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer Peter J. Kahrilas, MD - Gastroenterology
Last Updated April 11, 2008

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