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.
Alkaline diet
Urinary and/or saliva testing for acidity has been proposed as a way to measure the body's acidity level and therefore the level of risk for diseases. However, there is no correlation between the urinary pH and the acidity of the body.