Gastric acid
The highest concentration that gastric acid reaches in the stomach is 160 mM in the canaliculi. This is about 3 million times that of arterial blood, but almost exactly isotonic with other bodily fluids. The lowest pH of the secreted acid is 0.8, but the acid is diluted in the stomach lumen to a pH between 1 and 3.
Fecal pH test
Unhealthy individuals with a higher or lower pH rate have been observed having a higher mortality rate. A high alkaline pH rating being associated with the body's inability to create enough acid along with undigested food.