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 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.
Many medicines can change the results of this test. Be sure to tell your doctor about all the non-prescription and prescription medicines you take, especially acid-reducing medicines, such as Losec, Pepcid, Rolaids, Tums, or Zantac. 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.
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 mean. To help you understand the importance of this test, fill out the medical test information form .
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 a 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.
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 normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Normal values may be higher in very young children and older adults.
Many conditions can change gastrin levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.
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 before the test.
- Drinking caffeinated beverages or alcohol right before the test.
- Taking some medicines. Examples of medicines that can affect results include medicines that reduce stomach acid (such as Losec, Pepcid, or Zantac) and medicines or supplements that contain calcium (such as Tums or a daily vitamin). Make sure your doctor knows about all the medicines, herbs, and supplements you take.
- 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 millilitre (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
Citations
-
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Credits
Current as of:
September 23, 2020
Author: Healthwise Staff
Medical Review:
Adam Husney MD - Family Medicine
Anne C. Poinier MD - Internal Medicine
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Jerome B. Simon MD, FRCPC, FACP - Gastroenterology
