It’s a simple blood test that checks for excess gastrin production. Gastrin is a hormone that your stomach makes to fuel the release of gastric acid. Your body needs this to digest and absorb nutrients in your food, particularly proteins and amino acids. Your stomach makes 2 to 3 liters of acidic fluid a day.
Gastric acid is found inside cells called G cells. These are located in your stomach lining and in the lining of your upper small intestine.
Why Would I Need This Test?
Your doctor might order a gastrin test if they think you have a problem with your gastrin levels. If they’re too high or too low, you could have problems with your digestion. You may need the test if you have symptoms like stomach pain, diarrhea, or peptic ulcers that keep coming back.
Your doctor might also order a gastrin test if you had a gastrin-producing tumor removed and they want to make sure it hasn’t come back.
Preparing for the Test
You’ll need to fast for 12 hours beforehand. You can drink water but don’t eat any food during this time. You should also avoid drinking alcohol for at least 24 hours before the test. Be sure to tell your doctor about any medicines or supplements you take, including vitamins and herbs, as well as prescription and over-the-counter medications, or illegal drugs. You may need to stop taking some medications before the test.
Certain factors can affect your test results. Be sure to talk to your doctor if you:
- Have had or are planning to have peptic ulcer surgery
- Eat a high-protein diet
- Have diabetes and take insulin
- Take calcium supplements, antacids, or other medicines that can affect your ability to produce gastric acid
- Drink caffeine
- Take antidepressants
Results
Many factors can affect your test results. They might also vary based on the lab and the reference ranges they use. In general, the normal range for gastrin levels is:
- 0-180 pg/mL (picograms per milliliter of blood) for adults (this may be higher in older adults)
- 0-125 pg/mL for children
A gastrin level that’s too high may be caused by a condition called Zollinger-Ellison (ZE) syndrome. This could mean you have a tumor in your digestive system that’s secreting gastrin. These tumors are called gastrinomas. They’re normally located in the first part of your small intestine (the duodenum) or in your pancreas. The extra gastrin can cause too much acid in your digestive system. This can trigger diarrhea and may lead to ulcers in your stomach and small intestine.
By far, the two most common causes of high gastrin levels are anti-acid medications you take for reflux or heartburn and a condition called chronic atrophic gastritis. These both can do damage to your stomach lining. They also cause your stomach to make less acid. In these settings, the gastrin level increases because the pH of your stomach is too high (alkaline). The pH scale measures how acidic something is.
If you had a gastrinoma that was removed through surgery and your test results show an increase in gastrin, it may mean the tumor has returned. If your gastrin levels didn’t go down at all after surgery, it could mean the procedure wasn’t successful.
It’s rare to have gastrin levels that are too low. But if they are, your stomach might not absorb nutrients properly. You might also have a higher risk for infection in your digestive system.
Gastrin levels in the normal or low ranges usually aren’t cause for concern.