Pepsinogen (I and II)
A blood test that reflects the health of the stomach lining. Pepsinogens are precursors of a stomach digestive enzyme; a low pepsinogen I level and a low pepsinogen I to II ratio suggest the lining has thinned (atrophic gastritis), which raises the long-term risk of stomach cancer.
What it measures
Pepsinogens are inactive precursors of pepsin, an enzyme the stomach makes to digest protein. They come in two forms: pepsinogen I is produced only by the acid-secreting cells in the main body of the stomach, while pepsinogen II is made more widely. A small amount leaks into the blood, so measuring both — and especially their ratio — gives a window onto the state of the stomach lining without an endoscopy. The key pattern is a low pepsinogen I together with a low pepsinogen I/II ratio, which indicates that the specialised acid-producing lining has thinned or been lost — a condition called atrophic gastritis, often the result of long-standing Helicobacter pylori infection or an autoimmune process. This matters because atrophic gastritis reduces stomach acid (contributing to poor absorption of iron and vitamin B12) and, over years, carries an increased risk of stomach cancer. Pepsinogen testing is therefore used as a non-invasive way to flag people who may have this change and might benefit from endoscopy and surveillance. It is a risk marker and screening aid, not a diagnosis in itself.
What a high value can mean
- A high pepsinogen (often with high pepsinogen II) — can reflect active inflammation of the stomach, such as H. pylori gastritis or acid-related conditions.
- It is usually the low pattern, not the high one, that carries the important warning.
What a low value can mean
- Atrophic gastritis — a low pepsinogen I and a low I/II ratio suggest the stomach lining has thinned.
- Increased long-term stomach cancer risk — the reason the test is used as a marker.
- Reduced stomach acid — can impair absorption of iron and vitamin B12.
- Autoimmune (pernicious anaemia) or H. pylori-related atrophy — the common underlying causes.
When to discuss with a doctor
Pepsinogen is a risk marker for the state of the stomach lining rather than a routine test. The pattern to note is a low pepsinogen I with a low pepsinogen I/II ratio, which points to atrophic gastritis — a thinning of the stomach lining that reduces acid, can contribute to iron and vitamin B12 deficiency, and over years raises the risk of stomach cancer. A result suggesting atrophy usually leads to further assessment such as endoscopy, testing for H. pylori, and sometimes ongoing surveillance, guided by a doctor. It is always interpreted together with symptoms, H. pylori status and other results, not on its own. Mediora.AI shows pepsinogen alongside B12 and iron markers so the atrophic-gastritis pattern is visible; the interpretation and any follow-up belong with your doctor.