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.
Hyperchlorhydria
In humans, the normal pH is around 1 to 3, which varies throughout the day. The highest basal secretion levels are in the late evening (around 12 A.M. to 3 A.M.). Hyperchlorhydria is usually defined as having a pH less than 2. It has no negative consequences unless other conditions are also present such as gastroesophageal reflux disease (GERD).