Gastrin
A stomach hormone that tells the stomach to make acid. The blood test is done after fasting and is read alongside acid-reducing medicines and other results.
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What it is
Gastrin is a hormone made by special cells in the lower part of the stomach. It is released when food reaches the stomach and tells the stomach to make acid. As the acid level rises, the body normally makes less gastrin. This test measures gastrin in the blood after an overnight fast, when levels should be at their lowest.
Why it matters
Gastrin helps show what is going on with stomach acid. Levels go up when the stomach makes too little acid, because the brake on gastrin is missing, and when acid-reducing medicines are used. Much more rarely, a tumor that makes gastrin causes too much acid and ulcers. Because the common causes are so much more frequent than the rare one, the result is read together with your medicines, your symptoms and other tests.
If it’s high
A high gastrin is most often explained by acid-reducing medicines or by long-term inflammation of the stomach lining. In one UK study of about 1,000 people who had a stomach endoscopy, the median fasting gastrin was about 46 pmol/L in people taking a proton pump inhibitor and 20 pmol/L in people with a normal stomach. Much more rarely, a gastrin-making tumor (Zollinger-Ellison syndrome) is the cause. Doctors think of it mainly when gastrin is very high, for example above 1,000 pg/mL, together with high stomach acid. Your clinician will read the result in context.
Common causes
- Acid-reducing medicines, including proton pump inhibitors, H2 blockers and antacids
- Long-term inflammation or thinning of the stomach lining (atrophic gastritis), including pernicious anemia
- Helicobacter pylori infection of the stomach, which usually raises gastrin only slightly
- Reduced kidney function (chronic kidney disease)
- Previous stomach surgery, or a stomach outlet that is partly blocked
- Overactive gastrin-making cells in the stomach (G-cell hyperplasia)
- Rarely, a gastrin-making tumor (Zollinger-Ellison syndrome)
What can help
- Ask your clinician whether an acid-reducing medicine could explain the result
- Ask whether the test should be repeated and how to prepare for it
- Talk with your clinician before changing any acid-reducing medicine, because stopping some of them suddenly can cause problems
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 0–115 pg/mL. Source: Labcorp, MedlinePlus Medical Encyclopedia (National Library of Medicine), World Journal of Gastroenterology.
- 16+ (this one applies)0–115 pg/mL
Sources: Labcorp, MedlinePlus Medical Encyclopedia (National Library of Medicine), World Journal of Gastroenterology
What can affect your result
- Fasting: Labcorp asks for 12 to 14 hours without food, and eating makes gastrin rise
- Acid-reducing medicines raise it, and caffeine and corticosteroids can lower it
- Age: Labcorp prints different ranges for infants and children
- Kidney function: chronic kidney disease can raise it
- Units: some labs report pmol/L, and MedlinePlus gives 100 pg/mL as about 48 pmol/L
- Antacids, H2 blockers and proton pump inhibitors raise gastrin. Do not stop any of them unless your clinician tells you to.
- Caffeine and corticosteroids can lower gastrin (MedlinePlus).
- Labcorp notes that high-dose biotin supplements can interfere with its gastrin test. Tell your clinician or the lab if you take biotin.
- Labcorp rejects samples from people who were not fasting, hemolyzed or very fatty (lipemic) samples, plasma, and serum that arrives unfrozen.
Morning, after an overnight fast The result is a snapshot of one fasting morning and shows the effect of any acid-reducing medicine you take at the time.
When to talk to a clinician
Get urgent medical care for signs of stomach bleeding: black or tarry stool, vomiting blood or vomit that looks like coffee grounds, sudden severe belly pain, or dizziness or fainting. Talk with your clinician soon about a gastrin above about 1,000 pg/mL, or about any high result along with repeated ulcers, ongoing diarrhea or heartburn that does not settle.
Questions you could ask
- Why was this test ordered, and which other results should I look at with it?
- Could my acid-reducing medicine explain this result?
- Should this test be repeated, and how should I prepare for it?
- Do I need other tests, such as for H. pylori infection or vitamin B12?
Questions people ask
Why do I have to fast before a gastrin test?
Gastrin is released when food reaches the stomach, so a sample taken after eating can look high even when nothing is wrong. Labcorp asks for 12 to 14 hours of fasting and rejects samples from people who were not fasting.
Can my heartburn medicine make my gastrin high?
Yes. Proton pump inhibitors, H2 blockers and antacids can all raise gastrin. In one large study, people taking a proton pump inhibitor had a median fasting gastrin more than twice that of people with a normal stomach. Ask your clinician before changing any medicine.
Does a high gastrin mean I have a tumor?
Almost always not. Medicines and long-term stomach inflammation are far more common causes. A gastrin-making tumor is rare, about 1 to 1.5 cases per million people each year. Clinicians look for it mainly when gastrin is very high along with high stomach acid, repeated ulcers or ongoing diarrhea.
Show the science and sources
Units
- 1 pg/mL = 1 pg/mL
- 1 pg/mL = 1 ng/L
- 1 pg/mL = 0.4766 pmol/L
Open the Gastrin unit converter
For clinicians and researchers
Gastrin is a peptide hormone secreted by antral G cells. It stimulates gastric acid production, antral motility, and secretion of pepsin and intrinsic factor, and acid in the stomach normally suppresses its release. It circulates in several forms, for example G-34 ('big gastrin') and shorter forms such as G-17 ('little gastrin'), and each can be sulfated or non-sulfated (Labcorp), so assays and the pg/mL to pmol/L conversion are approximate. Labcorp uses an immunochemiluminometric assay on frozen serum after a 12 to 14 hour fast. Interpretation depends on gastric pH. 'Appropriate' hypergastrinemia occurs with low acid (atrophic gastritis with or without pernicious anemia, acid suppression, chronic kidney disease, H. pylori pangastritis, vagotomy). 'Inappropriate' hypergastrinemia occurs with high acid (Zollinger-Ellison syndrome, antral-predominant H. pylori infection, retained antrum, gastric outlet obstruction, extensive small-bowel resection). A 2021 review gives normal fasting gastrin as under 100 pg/mL, levels above 300 pg/mL as highly suspicious, and above 1,000 pg/mL with gastric pH below 2 as diagnostic of gastrinoma. Labcorp states that above 1,000 pg/mL with basal acid output above 15 mmol/hour in an unoperated ulcer patient establishes the diagnosis, but that up to 40% of patients with Zollinger-Ellison syndrome have fasting values of 100–500 pg/mL and at least half lack diagnostic levels. When a tumor is likely but the fasting level is not diagnostic, the secretin stimulation test is the usual next step, and it can give false positives in pernicious anemia and with chronic PPI use. Fasting gastrin and gastric pH are best measured off PPIs, but stopping a PPI can be dangerous in patients with Zollinger-Ellison syndrome, so the timing is individualized. Zollinger-Ellison syndrome has an incidence of about 1 to 1.5 cases per million per year. In that UK study (982 people analysed, radioimmunoassay), 44% of PPI users still had fasting gastrin under that assay's upper limit of 40 pmol/L, and 17% had values above 100 pmol/L.
LOINC 2333-3 (primary), 15072-2, 29395-1. Specimen: serum.
Sources
- Gastrin, Serum (test 004390), Labcorp
- Gastrin blood test, MedlinePlus Medical Encyclopedia (National Library of Medicine)
- Gastrinoma and Zollinger Ellison syndrome: A roadmap for the management between new and old therapies, World Journal of Gastroenterology (2021)
- Effects of Proton Pump Inhibitor Therapy, H. pylori Infection and Gastric Preneoplastic Pathology on Fasting Serum Gastrin Concentrations, Frontiers in Endocrinology (2021)
- Gastrin-17 (PubChem compound 16162108), molecular weight 2098.2, PubChem (National Library of Medicine)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.